Learn how to make a beautifully colorful rainbow cake, as tall or as short as you want it to be. Find instructions for scaling cake to your needs and how to efficiently create 6 layers of cake, even if you only have 2 pans.
6Tablespoons(85g) unsalted buttersoftened to room temperature1
½cup(120mL) heavy creamroom temperature1,2
3large egg whitesroom temperature1
1 and ¼teaspoonsvanilla extract
food coloring in desired colors3see notes for colors I used
WHIPPED CREAM BUTTERCREAM
4cups(480g) powdered sugar
1cup(227g) unsalted buttersoftened to room temperature
⅓cup(80mL) heavy whipping cream
CAKE (PER TWO 6" LAYERS)
Place oven rack on the middle setting and preheat the oven to 350ºF (177ºC). Grease and flour (or use homemade cake release) two 6" round cake pans.
Set out two empty medium size bowls.
In one medium size bowl, combine the flour, cornstarch, sugar, baking powder, and salt. Blend ingredients together with a whisk or fork until completely combined. Set aside.
In the other empty bowl, combine the heavy cream, egg whites, and vanilla extract and mix gently with a fork until blended. Set aside.
Transfer the dry ingredients to a large bowl (if using a handheld mixer) or the bowl of a stand mixer fitted with the paddle attachment, but do not discard the medium bowl. Add the room temperature butter and beat mixture on low speed until it resembles sand. Scrape down the sides and bottom of the bowl with a spatula and mix again on low for a few seconds until thoroughly combined.
Turn the mixer speed up to medium-low, add half of the milk mixture (about 1/2 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 two medium size bowls (that are now dirty). Add a bit of food coloring in the color of your choice to one of the small bowls, stir, and add more coloring until it is to your liking. Repeat with the second bowl and a second coloring. I did red and orange together, yellow and green together, and blue and purple together.
Bake cakes for about 23-25 minutes or until a toothpick inserted in the center comes out clean. Remove from oven and allow cakes to cool at least 15-20 minutes (preferably longer) on a wire rack before removing from pans and moving on to the next batch of colors.
In a large bowl with a handheld mixer, or a stand mixer fitted with the paddle attachment, beat the butter on medium speed until creamy, about 2 minutes.
With the mixer on low, add in the powdered sugar, vanilla and almond extracts, and salt. Add the cream and continue to mix until everything starts to come together.
Increase mixer speed to high and beat for 3-4 minutes until frosting is fluffy, pausing once or twice to scrape down the sides and bottom of the bowl. Be careful not to over-beat the frosting, as whipping cream may start to clump. Decrease mixer speed to low if you need to add more cream to thin to desired texture.
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.
Room temperature ingredients: it is imperative to use room temperature ingredients in this recipe. Allow ingredients to sit out at room temperature at least 45 minutes before beginning.
Heavy cream: I strongly encourage using cream in this recipe. It keeps the crumb moist and dense and adds a creaminess to the overall texture of the cake.
Food coloring: I prefer gel food coloring. My favorite is AmeriColor.
Recipe adapted from White Layer CakeIf you want this cake to be 8" in diameter, double the cake recipe for each pair of layers and do 1 and ½ times the recipe written for the buttercream.I used the following color names for my layers: super red, orange, egg yellow, leaf green, royal blue, and combination of violet + a touch of electric pink.