Description

This vibrant Rainbow Cake recipe features six colorful layers stacked with a rich and creamy vanilla buttercream frosting. Perfect for celebrations or any occasion needing a show-stopping dessert, this cake is as delightful to look at as it is to eat. The recipe includes detailed instructions on creating colorful batter layers and fluffy frosting to achieve a moist and stunning rainbow cake.

Ingredients

Scale

Dry Ingredients

2½ cups all-purpose flour (350 grams)
1½ cups granulated sugar (300 grams)
1 teaspoon baking soda (6 grams)
1 teaspoon baking powder (4 grams)
½ teaspoon kosher salt

Wet Ingredients

1½ cups buttermilk (341 grams, room temperature)
½ cup unsalted butter (115 grams, slightly melted)
3 large eggs (150 grams, room temperature)
2 teaspoons pure vanilla extract (8 grams)

Coloring

Gel food coloring (red, orange, yellow, green, blue, purple)

Buttercream Frosting

5 cups powdered sugar (600 grams)
1½ cups unsalted butter (340 grams, slightly melted, about 3 sticks)
1 tablespoon pure vanilla extract (12 grams)

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Instructions

Prepare the batter: Preheat the oven and grease six 8-inch round cake pans. In a large bowl, whisk together the all-purpose flour, granulated sugar, baking soda, baking powder, and kosher salt. In another bowl, combine the buttermilk, slightly melted unsalted butter, eggs, and vanilla extract until well blended. Gradually add the wet ingredients to the dry ingredients and mix until smooth and just combined.
Divide and color the batter: Divide the batter evenly into six separate bowls. Add gel food coloring to each bowl to create red, orange, yellow, green, blue, and purple batters. Mix each until the color is vibrant and uniform.
Bake the cake layers: Pour each colored batter evenly into the prepared cake pans. Bake in the preheated oven at 350°F (175°C) for about 18–20 minutes or until a toothpick inserted in the center comes out clean. Allow the cake layers to cool completely in the pans, then carefully remove them.
Make the buttercream frosting: In a large bowl, beat the slightly melted unsalted butter until creamy. Gradually add the powdered sugar, mixing on low speed to avoid a sugar cloud. Add the vanilla extract and continue to beat on medium-high speed until the frosting is light, fluffy, and smooth.
Assemble the cake: Place the purple layer on a cake board or serving plate. Spread an even layer of buttercream on top, then add the blue layer. Repeat with green, yellow, orange, and finally the red layer on top. Spread a thin crumb coat of frosting over the entire cake and chill for 15-20 minutes. Finish frosting the top and sides evenly with the remaining buttercream.
Decorate and serve: Optionally, decorate the cake with sprinkles or edible glitter. Slice the cake into 10 generous slices and serve. Store leftovers covered in the refrigerator for up to 3 days for best freshness.

Notes

Ensure all ingredients, especially eggs and buttermilk, are at room temperature for the best batter consistency.
Use gel food coloring to achieve vibrant colors without altering batter consistency.
You can substitute buttermilk with milk and 1 tablespoon vinegar or lemon juice if necessary.
Allow cake layers to cool completely before frosting to prevent melting.
For easier slicing, chill the cake for 30 minutes before cutting.