Rainbow Cake Recipe

This show-stopping rainbow cake is perfect for everything from birthdays to holidays. This colorful cake is moist and flavorful and can be paired with any buttercream or frosting you like. You can even use a box mix, if you prefer.

Instructions

CAKE

Place oven rack on the middle setting and preheat the oven to 350ºF (177ºC). Line as many 6" cake pans⁴ as you have available with parchment rounds. See post above for details about this.
Set out six empty medium size bowls.
In a large bowl with a handheld mixer or the bowl of a stand mixer fitted with the paddle attachment, combine the flour, cornstarch, sugar, baking powder, and salt. Blend ingredients together on low until completely combined, about 1 minute.
2 cups (240g) all-purpose flour, 2 Tablespoons (15g) cornstarch, 1 and ¾ cup (350g) granulated sugar, 4 teaspoons baking powder, 1 teaspoon salt
Add the room temperature butter and beat mixture on low speed until it resembles sand (see photo in post text). Scrape down the sides and bottom of the bowl with a spatula and mix again on low for a few seconds until thoroughly combined.
12 Tablespoons (171g) unsalted butter
Combine the whole milk, egg whites, and vanilla extract in a large container with a spout (like a 2-cup glass measuring cup) and mix gently with a fork until blended.
1 cup (240mL) whole milk, 6 large egg whites, 2 and ½ teaspoons vanilla extract
With the mixer speed on medium-low, add half of the milk mixture (about 1 cup) to the crumb mixture and mix until blended. Add the remaining milk mixture to the batter and beat again on medium-low until everything is incorporated. Turn the mixer off, scrape down the sides and bottom of the bowl with a spatula, and increase mixer speed to medium. Beat the batter for about 30 seconds until batter is smooth.
Divide batter evenly between the six medium size bowls. My batter worked out to be exactly 200g of batter for each color/layer. Add food coloring to each bowl, and stir until color is blended evenly.
food coloring in desired colors3
Pour the batter into the prepared cake pans, reserving any remaining colors until you have more pans available. Bake cakes for 15-18 minutes or until a toothpick inserted in the center comes out clean and the tops spring back when you touch them. Remove from oven and allow cakes to cool in the pans for about 10 minutes before removing and moving on to the next batch of colors.

BUTTERCREAM

In a large bowl with a handheld mixer or a stand mixer fitted with the paddle attachment, beat the the butter on medium-high until smooth, about 2 minutes.
1 cup (227g) unsalted butter
Reduce the mixer to low, then slowly add the powdered sugar and mix until everything is combined. Add the vanilla extract and mix again.
4 cups (480g) powdered sugar, 1 teaspoons vanilla extract
Slowly add the milk or cream, watching for and stopping at desired consistency. Add the salt, then increase the mixer speed to medium and beat until completely smooth.
¼ to ⅓ cup (30-80mL) milk or cream, ¼ teaspoon salt
If after beating, the frosting is too stiff, add more cream. If it is too thin, add more powdered sugar, about 2 Tablespoons at a time.
Turn off the mixer and use a spatula to stir the buttercream by hand to remove air bubbles and make it smooth and creamy. This usually takes about 3-5 minutes, but can take longer, especially if your mixer is very strong. Cover tightly and store at room temperature until ready to use.

ASSEMBLE THE CAKE

Trim your cake layers to the desired height, keeping in mind that their height x 6 layers will be the total height of your cake.
Place the layer in the color you want on the bottom on a plate or cake stand. Using a spatula or knife, spread an even layer of frosting over the entire surface. Place the next layer in the color you want second to last on top, and press down on the top lightly. Continue stacking layers of cake until you reach the beginning of the rainbow and have used all of your layers. Spread the rest of the frosting on the cake, beginning with the top and working your way down the sides. Decorate as desired.
Cake stays fresh covered at room temperature for up to 4 days. Cake may be covered and refrigerated for up to 7 days.

Ingredients

CAKE

VANILLA BUTTERCREAM

Instructions

CAKE

BUTTERCREAM

ASSEMBLE THE CAKE

Notes

Nutrition Disclosure