Name: Rainbow Surprise Bundt Cake Recipe
Prep time: 45 min
Cook time: 45 min
Total time: 1 h 15 min
Cuisine: American
Ingredients: 260 g all purpose flour; 100 g cake flour; 2 tsp baking powder; 1 tsp fine sea salt; 226 g unsalted butter, softened; 75 g coconut oil; 400 g fine granulated sugar; 2 tsp pure vanilla extract; 1 tsp imitation vanilla; 4 large egg whites; 240 g buttermilk; Gel food coloring in red, yellow, green, blue, and purple

Imagine slicing into a classic white bundt cake, only to reveal a vibrant, colorful rainbow swirl hidden inside—it’s like a party in every slice! That’s exactly what this Rainbow Surprise Bundt Cake Recipe delivers: moist, tender cake with a whimsical twist perfect for brightening any celebration.

A round bundt cake sits on a white pedestal cake stand with white icing dripping smoothly down the sides and golden sprinkles scattered on top. One slice is removed, showing a rainbow pattern inside with red, orange, yellow, green, blue, and purple layers arranged in an arch shape surrounded by light beige cake. Two slices with the same rainbow pattern lie on white plates in front of the cake stand, with golden sprinkles scattered around the plates. A small white pitcher holds some more white icing, and a glass jar filled with golden sprinkles sits nearby on a white marbled surface. Photo taken with an iphone --ar 2:3 --v 7

Jump to:

Why You'll Love This Recipe
Ingredients & Why They Work
Make It Your Way
Step-by-Step: How I Make Rainbow Surprise Bundt Cake Recipe
Top Tip
How to Serve Rainbow Surprise Bundt Cake Recipe
Make Ahead and Storage
Frequently Asked Questions:
Final Thoughts
Rainbow Surprise Bundt Cake Recipe

Why You'll Love This Recipe

I first made this cake when I wanted something classic yet surprising for my best friend’s birthday. Watching her face light up when the rainbow appeared inside was totally worth the little extra effort—promise you’ll feel the same joy!

Unexpected Wow Factor: The hidden rainbow inside makes a simple bundt cake truly memorable.
Moist & Tender Texture: The mix of butter and coconut oil creates a rich yet soft crumb.
Vibrant, Natural Colors: Using gel food coloring keeps the batter smooth and beautifully bright.
Perfect for Any Celebration: From birthdays to baby showers, it’s a crowd-pleaser every time.

Ingredients & Why They Work

When it comes to this Rainbow Surprise Bundt Cake, I always recommend starting with high-quality ingredients—you’ll taste the difference. Here’s a quick run-down on what you’ll need and why each part is important.

Flat lay of a small mound of all purpose flour, a small mound of cake flour, a few cubes of softened unsalted butter, a small pool of coconut oil in a white ceramic bowl, a small pile of fine granulated sugar, a pinch of fine sea salt on a white ceramic dish, two small white ceramic bowls each holding clear vanilla extract and imitation vanilla, a white ceramic bowl with baking powder, four large whole brown eggs with clean shells, a small white ceramic bowl filled with buttermilk, all ingredients arranged with perfect symmetry and balanced proportions, placed on a clean white marble surface, soft natural light, photo taken with an iPhone, professional food photography style, fresh ingredients, white ceramic bowls, no bottles, no duplicates, no utensils, no packaging --ar 2:3 --v 7 --p m7354615311229779997

All purpose flour: Provides structure and a tender crumb that holds the cake together perfectly.
Cake flour: Adds extra softness, making the texture lighter and more delicate.
Unsalted butter: Creamed to fluffy perfection, it imparts richness and flavor.
Coconut oil: Adds moisture and a subtle tropical note that complements the vanilla beautifully.
Fine granulated sugar: Sweetens evenly and assists in creating a light cake crumb.
Fine sea salt: Enhances all the other flavors without overpowering them.
Pure vanilla extract: Brings deep, natural vanilla flavor, one of the cake’s star tastes.
Imitation vanilla: A budget-friendly backup that adds an extra layer of vanilla aroma.
Baking powder: Essential for leavening to make the cake rise and be airy.
Large egg whites: Whipped into the batter carefully to add lightness and structure.
Buttermilk: Adds acidity that tenderizes the crumb and gives a slight tang for balance.
Gel food coloring (red, yellow, green, blue, purple): For those bright, clean colors without watering down the batter.

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Note: You'll find the complete list of ingredients, along with their exact measurements, in the printable recipe card at the bottom of this post.

Make It Your Way

The beauty of this Rainbow Surprise Bundt Cake Recipe is how easy it is to personalize. Whether you want to play with colors, flavors, or dietary tweaks, you can make this cake uniquely yours while keeping its magical rainbow core.

Dairy-Free Version: Swap the butter and buttermilk for your favorite non-dairy alternatives like vegan butter and almond milk mixed with a splash of apple cider vinegar. I tried this for a friend who’s lactose intolerant, and the cake still turned out moist and colorful!
Flavor Twists: Add a teaspoon of lemon zest or a hint of almond extract to the batter for a subtle flavor boost that complements the vanilla perfectly. The lemon zest really brightened up the layers in my last bake.
Color Variations: Have fun switching up the rainbow colors with pastel tones or even a seasonal palette like autumn hues (think burnt orange, deep red, golden yellow). It’s a great way to match the cake to any celebration or holiday theme.
Gluten-Free Adjustments: Use a gluten-free all purpose flour blend instead of regular flour to make this bundt cake suitable for gluten-sensitive guests. Just be sure to pick one that includes xanthan gum for the best texture.
Frosting Fun: While the cake is stunning on its own, a light dusting of powdered sugar, a simple vanilla glaze, or even a cream cheese frosting can add an extra layer of indulgence. I recommend a thin glaze to keep the focus on the rainbow surprise inside.

Step-by-Step: How I Make Rainbow Surprise Bundt Cake Recipe

A clear glass bowl sits on a white marbled surface, holding a crumbly light yellow dough mixture. Inside the bowl, two beaters coated with the same dough are visible, one close to the bowl's edge and the other more centered, both with a textured, soft appearance. There are small bits of dough stuck to the bowl's sides. The lighting highlights the creamy texture of the dough and the smooth glass reflecting some light. photo taken with an iphone --ar 2:3 --v 7

Step 1: Preheat and Prep Your Bundt Pan

Start by preheating your oven to 350 degrees Fahrenheit. Thoroughly butter and flour a large bundt pan to make sure your cake won’t stick. This step is key for an easy release, especially with all those vibrant layers inside.

Step 2: Sift Together Your Dry Ingredients

In a medium bowl, sift the 260 grams of all purpose flour and 100 grams of cake flour together, then add 2 teaspoons of baking powder and 1 teaspoon of fine sea salt. Setting this aside makes it easy to incorporate later without lumps in your batter.

Step 3: Cream Butter, Coconut Oil, and Sugar

Using a mixer, cream together 226 grams of softened unsalted butter, 75 grams of coconut oil, 400 grams of fine granulated sugar, 1 teaspoon of fine sea salt, 2 teaspoons pure vanilla extract, 1 teaspoon imitation vanilla, and the baking powder for a full five minutes. You’ll know it’s ready when the mixture turns very light and fluffy—this is what gives your cake that tender texture.

Step 4: Add Egg Whites One by One

With the mixer running on low, add 4 large egg whites one at a time. Pause after each addition to fully incorporate it before adding the next. This slow incorporation helps trap air, keeping your batter airy and light.

Step 5: Combine Flour Mixture and Buttermilk

Add the sifted flour mixture to your wet ingredients. Turn the mixer to low and slowly drizzle in 240 grams of buttermilk. Mix just until everything is well combined and smooth—overmixing can toughen the cake, so be gentle here.

Step 6: Divide and Color the Batter

Divide your batter equally into five small bowls, about ⅓ cup each. Add gel food coloring to each bowl to create red, yellow, green, blue, and purple batters. Stir until the colors are vibrant and even. This step is where the magic starts to form!

Step 7: Fill the Bundt Pan with White Batter

Pour more than two-thirds of the remaining white batter (the uncolored portion) into your prepared bundt pan. Be sure to save the last bit of batter to cover the colorful layers later—this helps keep the rainbow surprise intact during baking.

Step 8: Pipe the Rainbow Pattern

Transfer each colored batter into separate piping bags and snip off the tips. Using the back of a teaspoon, create a small moat in the center of the white batter where you’ll pipe your rainbow rings. Start with the red batter, piping a circle into that moat, then gently smooth it with the back of the spoon to make it wide—just leave white borders inside and outside.

Continue piping the yellow, then green, blue, and purple rings, each a little narrower than the last. The goal is well-defined color rings that don’t blend into each other. Take your time with this step; it really brings the surprise to life!

Step 9: Cover the Rainbow and Bake

Spoon the reserved white batter carefully over your colorful rings with an offset spatula. Be gentle to avoid smushing the layers. Then pop your bundt cake in the oven and bake for about 45 minutes. Start checking around 40 minutes by gently pressing the cake—if it springs back, it’s ready!

Step 10: Cool and Reveal Your Rainbow Surprise

Once baked, let the cake cool in the bundt pan for 15 minutes. This resting time helps the cake firm up, making it easier to unmold. Then carefully invert the pan onto a cooling rack to finish cooling completely. When you slice it, get ready to delight in the hidden rainbow magic inside!

Top Tip

These tips will help you create the most stunning and delicious Rainbow Surprise Bundt Cake every time, so your colorful masterpiece turns out beautifully and tastes just right!

Softening Butter Completely: Make sure your butter is fully softened before creaming. It makes a huge difference in achieving that light, fluffy texture which helps the cake rise perfectly.
Gentle Layering: >When piping the colored batter rings, be patient and gentle to keep the rainbow pattern distinct. This was a game-changer for me after some early attempts where colors blended too much.
Using Gel Food Coloring: Gel colors give you those vibrant hues without thinning out the batter, ensuring each slice’s surprise is bright and delightful.
Cooling Time: Don’t rush unmolding. Letting the cake cool for about 15 minutes in the pan before turning it out helps prevent any cracks or breaks—trust me, it’s worth the wait!

How to Serve Rainbow Surprise Bundt Cake Recipe

This image shows a round wooden plate with several slices of cake arranged in a circular pattern. Each slice has a thick layer of purple frosting on top, decorated with small golden sprinkles shaped like cones and tiny white sprinkles. Inside the cake, there are colorful rainbow layers visible, starting with pink near the bottom, then blue, green, and yellow forming an arched shape on the light beige cake. The plate is placed on a white marbled surface, and more golden cone-shaped sprinkles are scattered around it. Photo taken with an iphone --ar 2:3 --v 7

Garnishes

The Rainbow Surprise Bundt Cake is a showstopper on its own, but simple garnishes can elevate it even more. Consider dusting with a light sprinkle of powdered sugar for an elegant touch or drizzling a vanilla glaze over the top to add a delicate sweetness that complements the white cake base. Fresh berries like raspberries or blueberries add a pop of natural color and a hint of tartness. For a festive celebration, edible glitter or rainbow sprinkles can add an extra sprinkle of magic!

Side Dishes

This dessert pairs wonderfully with a scoop of classic vanilla ice cream or a dollop of freshly whipped cream. A cup of robust coffee or a lightly brewed tea balances the sweetness perfectly, making it ideal for afternoon tea parties or celebratory brunches. For a fresh contrast, serve with a fruit salad featuring citrus or tropical fruits that brighten up the whole experience.

Make Ahead and Storage

Storing Leftovers

To keep your Rainbow Surprise Bundt Cake fresh, store any leftovers tightly wrapped in plastic wrap or in an airtight container at room temperature. It will stay delicious for 2 to 3 days this way. If your kitchen is warm, refrigeration is fine, but bring slices back to room temperature before serving for the best texture and flavor.

Freezing

You can freeze this cake comfortably for up to 2 months. Slice it beforehand for easy thawing, then wrap each piece tightly in plastic wrap and place in an airtight container or heavy-duty freezer bag. To thaw, transfer slices to the fridge overnight or leave out at room temperature for a couple of hours before serving.

Reheating

Since this bundt cake is best enjoyed at room temperature, reheating isn't usually necessary. But if you prefer it warm, gently heat individual slices in the microwave for about 10-15 seconds. Avoid overheating to keep the cake moist and preserve the vibrant colors inside.

Frequently Asked Questions:

Can I use regular food coloring instead of gel food coloring?

While regular liquid food coloring can work, gel food coloring is better for this Rainbow Surprise Bundt Cake Recipe because it provides vibrant colors without thinning the batter, helping maintain the perfect texture and distinct rainbow layers.

How do I know when the bundt cake is done baking?

Bake the cake for 45 minutes at 350°F, checking at 40 minutes. The cake is done when it springs back to a gentle touch and a skewer inserted in the cake comes out clean or with a few moist crumbs.

Can I make this cake gluten-free?

This recipe is designed with all purpose and cake flour for a tender crumb. You can try substituting a gluten-free flour blend, but results may vary, especially with the layering and texture. Adjustments might be needed.

What’s the best way to pipe the colored batter if I don’t have piping bags?

No piping bags? No problem! You can use small zip-top bags with a tiny corner cut off to pipe the colored batter. This method works well and gives you control over the batter placement.

Final Thoughts

Baking the Rainbow Surprise Bundt Cake Recipe is such a joyful experience—every slice feels like unveiling a little piece of magic. The moist, tender crumb combined with the unexpected burst of rainbow colors inside makes it truly memorable for any celebration or cozy gathering. Whether you’re baking it for a birthday, holiday, or just because, I hope it brings you as much happiness as it has for me. Happy baking and enjoy every colorful bite!