Most any grandmother will tell you: If you’re grandchild requests a rainbow cake for his fourth birthday, then, by golly, you’ll do everything in your power to make it happen.
Such was the case for me when I asked my grandson what kind of birthday cake he wanted. His answer? A rainbow cake! What, I wondered, is a rainbow cake? Maybe a chocolate cake with chocolate icing and a plastic rainbow decoration on top? Or what about going to the bakery and asking for one? Short of spending upward of $50 on a cake, I chose to look online and lo and behold, rainbow cakes are a “thing.”
It’s a multi-layered cake, every layer a different color. So that means making six layers and using lots of food coloring. When all was said and done, I was surprised how easy it was. Yes, it was a production, but using cake mix certainly reduced the amount of work and time in the kitchen. And it involved cleaning more bowls, because the any rainbow cake recipe calls for dividing the batter into six bowls so each one could be colored differently. I wanted to break out in song when the cakes came out correctly:
Red and yellow and pink and green, purple and orange and blue. I can sing a rainbow, sing a rainbow, sing a rainbow, too. Remember that one?
I used a recipe I’ve had for years, one that takes white cake mix to new heights with vegetable oil and sour cream, making it oh so moist. The icing was my favorite almond buttercream. To make things even easier, I made the layers a day ahead, wrapped them individually in plastic and refrigerated them overnight. It made icing them easier. The icing recipe makes just enough icing to spread thick layers between each cake layer. I wanted the colors to show, so I didn’t fully ice the sides, choosing a cake with a more “naked” look. If you want a fully iced cake, you’ll need to make extra icing.
When you cut into the cake and the first slice is revealed, you’ll be delighted at all the color. Use food coloring gel for more vibrant color.
Rainbow Cake With Almond Buttercream
2 boxes white cake mix
1 cup water
1 cup vegetable oil
16 oz sour cream
Gel food coloring
2 cups unsalted butter room temperature
5 cups powdered sugar
2 teaspoons almond extract
1 teaspoon vanilla extract
½ teaspoon salt
¼ cup heavy cream
Preheat the oven to the temperature on the back of the cake box. Prepare and grease six cake cake pans (see note). Set aside.
In a large bowl, combine the cake mix, water, vegetable oil, sour cream and eggs. Mix well to combine.
Evenly distribute the batter into six bowls to make all of the colors. Add the desired amount of food coloring to each bowl and mix until the color is smooth.
Add the batter to the pan for each color and bake according to the package on the back of the cake mix box.Let the cake cool completely before frosting the cake with buttercream frosting. Frost the cake, first with a crumb coat, and then with the remaining frosting. Top with sprinkles if desired.
To make buttercream: Place butter in stand mixer and mix on medium-high for a couple of minutes until really creamy. Add powdered sugar and extracts. Blend well. Add heavy cream and mix until frosting reaches desired consistency, adding a little more cream, as desired.
Note: I have two ovens, so I was able to bake several at a time. I only had four cake pans, so reused two of them once the first cakes were cooled and removed from the pans. Plan accordingly.