Rainbow Cake with Rainbow Buttercream

The ultimate colorful celebration cake

This Rainbow Cake with Rainbow Buttercream is the kind of dessert that instantly turns any celebration into something magical. With six vibrant cake layers inside, smooth rainbow-striped buttercream on the outside, and a swirl of fluffy frosting topped with rainbow sprinkles, this cake is bold, cheerful, and unforgettable. It’s perfect for birthdays, baby showers, pride celebrations, or any occasion that deserves a fun and eye-catching centerpiece.

What makes this recipe especially special is that it’s not just pretty it’s also delicious. The cake layers are soft, moist, and tender thanks to a bakery-style white cake base made with cake flour, egg whites, oil, butter, and buttermilk. The vanilla buttercream is creamy, fluffy, and sturdy enough for decorating, while still tasting rich and smooth with every bite.

Even though this cake looks elaborate, the process is very manageable when broken into steps. You’ll prepare one batter, divide it into six bowls, tint each portion a different color, and bake the layers separately. Then you’ll stack, frost, stripe, smooth, and decorate. The final reveal when you slice into it is always worth the effort.

If you’ve been searching for a show-stopping rainbow layer cake recipe with detailed formatting, Pinterest assets, FAQs, and HTML code, this one covers everything you need.

table of contents

Time Breakdown

Prep Time: 1 hour
Cook Time: 30 minutes
Cooling Time: 3 hours
Total Time: 4 hours 30 minutes
Servings: 20 slices

Ingredients List

For the Rainbow Cake

• 2 1/2 cups (265g) sifted cake flour
• 2 teaspoons baking powder
• 1/2 teaspoon baking soda
• 1/2 teaspoon salt
• 1 1/2 cups (300g) granulated sugar
• 1/2 cup (113g) unsalted butter, room temperature
• 4 large egg whites, room temperature
• 1/2 cup (120ml) vegetable oil
• 1 tablespoon pure vanilla extract
• 1 1/4 cups (300ml) full-fat buttermilk, room temperature
• Red food coloring
• Orange food coloring
• Yellow food coloring
• Green food coloring
• Blue food coloring
• Purple food coloring

For the Vanilla Buttercream

• 2 cups (452g) unsalted butter, room temperature
• 7 cups (840g) powdered sugar
• 4 teaspoons pure vanilla extract
• 1/4 cup whole milk, room temperature
• Pinch of salt, or to taste
• Red food coloring
• Orange food coloring
• Yellow food coloring
• Green food coloring
• Blue food coloring
• Purple food coloring

For Garnish

• 2 tablespoons rainbow sprinkles

Kitchen Tools You’ll Need

This recipe doesn’t require fancy gadgets, just a few reliable kitchen basics to keep everything simple and stress-free.

• Six 6-inch cake pans
• Parchment paper circles
• Stand mixer or hand mixer
• Mixing bowls
• Whisk
• Rubber spatula
• Kitchen scale
• Offset spatula
• Bench scraper or icing smoother
• Cake turntable
• Piping bags
• Tip 4B piping tip
• Cooling rack

Step-by-Step Beginner-Friendly Instructions

1. Prepare the pans and oven 🎂

Preheat your oven to 325°F (163°C). Spray the sides of six 6-inch cake pans with baking spray and line each bottom with a parchment paper circle.

2. Mix the dry ingredients

In a medium bowl, whisk together the cake flour, baking powder, baking soda, and salt until evenly combined. Set aside.

3. Cream the butter and sugar

In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on high speed for about 2 minutes until creamy. Add the sugar and beat on medium-high for about 2 more minutes until light and fluffy. Scrape down the bowl and paddle halfway through.

4. Add egg whites, oil, and vanilla

Turn the mixer to low and add the egg whites one at a time, mixing until just combined. Add the vegetable oil and vanilla extract, then increase the speed to high and beat for 1 minute until smooth and slightly fluffy.

5. Add dry ingredients and buttermilk

Turn the mixer off. Add the flour mixture all at once and mix on low just until combined. Slowly pour in the buttermilk and continue mixing on low for about 30 seconds until the batter is smooth and uniform. The batter will be slightly thin.

6. Divide and color the batter 🌈

Divide the batter evenly into six bowls. For best accuracy, use a kitchen scale and portion about 200g batter per bowl. Color each bowl one of the rainbow shades: red, orange, yellow, green, blue, and purple. Stir each color until fully incorporated.

7. Bake the cake layers

Pour each colored batter into its own prepared cake pan. Bake for 18 to 22 minutes, or until the layers spring back lightly when touched and a toothpick inserted in the center comes out clean.

8. Cool the cakes

Let the cakes cool in their pans for 5 minutes, then carefully remove them and place them on a wire rack to cool completely.

9. Make the vanilla buttercream

In a large bowl or stand mixer, beat the butter on medium-high speed for about 7 minutes, until very light, fluffy, and almost white in color. With the mixer on low, add powdered sugar one cup at a time, fully incorporating each addition before adding the next. Add vanilla, milk, and salt, then mix on low for 1 minute until smooth.

10. Stack and crumb coat

Once the layers are completely cool, level the tops if needed. Spread a small swipe of buttercream onto a cake board and place the first cake layer down. Stack the layers in reverse rainbow order, using a thin layer of buttercream between each. Place the final layer upside down on top for a cleaner finish. Apply a thin crumb coat around the whole cake, then refrigerate for 15 to 20 minutes.

11. Color the buttercream

Reserve about 1 cup of white buttercream for the top swirls. Divide the remaining buttercream into six bowls, tinting them red, orange, yellow, green, blue, and purple. Make the red bowl slightly larger since it covers the top and one stripe.

12. Create the rainbow stripe design 🌈

Place each buttercream color into its own piping bag and snip a 1/2-inch opening. Pipe horizontal stripes around the chilled cake, starting with purple at the bottom and continuing upward in rainbow order. Cover the top with red buttercream. Smooth the sides with an icing smoother and tidy the top with an offset spatula.

13. Add the swirl border and sprinkles ✨

Add the reserved white buttercream to a piping bag fitted with a Tip 4B. Pipe swirls around the top edge of the cake and immediately garnish with rainbow sprinkles.

Pro Tips Section

• For even layers: Weigh the batter in each bowl so your cake layers bake to the same height.
• For bold colors: Use gel food coloring instead of liquid food coloring for more vibrant shades without thinning the batter.
• For easy assembly: Chill the cake after the crumb coat so the striped buttercream glides on more smoothly.
• For make-ahead prep: Bake the layers a day or two ahead and wrap them tightly until ready to decorate.

Nutrition Table

Serving Size	Calories	Protein	Carbs	Fat	Fiber	Sugar
1 slice	420	4g	58g	20g	1g	45g

Disclaimer

Color intensity may vary depending on the brand of food coloring used. For the smoothest buttercream finish, use room-temperature ingredients and avoid over-thinning with extra milk.

Conclusion

This Rainbow Cake with Rainbow Buttercream is the kind of dessert that instantly makes people smile. From the bright six-layer rainbow interior to the striped buttercream finish and sprinkle-topped swirls, every part of this cake feels festive and fun. It’s soft, moist, colorful, and perfect for birthdays, parties, and any celebration that deserves a bold centerpiece. If you want a cake that tastes as amazing as it looks, this is the one to save.