1. Prepare the Cake Layers:
Preheat your oven to 350°F (175°C) and grease six 8-inch round cake pans (or bake in batches if you have fewer pans). Line the bottoms with parchment paper for easy release.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large mixing bowl, beat the butter and sugar together until light and fluffy (about 3 minutes).
Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.
Alternately add the dry ingredients and milk to the batter, beginning and ending with the dry ingredients. Mix until just combined.
Divide the batter evenly into six bowls. Add food coloring to each bowl to create vibrant red, orange, yellow, green, blue, and violet batters. Mix well.
2. Bake the Layers:
Pour each colored batter into its prepared pan. Smooth the tops with a spatula.
Bake for 15-18 minutes, or until a toothpick inserted into the center comes out clean.
Let the cakes cool in their pans for 10 minutes, then transfer to a wire rack to cool completely.
3. Make the Buttercream Frosting:
In a large bowl, beat the butter until creamy.
Gradually add the powdered sugar, mixing well after each addition.
Add the heavy cream, vanilla extract, and salt. Beat until the frosting is fluffy and spreadable.
4. Assemble the Cake:
Place the violet layer on a cake board or serving plate. Spread a thin layer of frosting on top.
Repeat with the blue, green, yellow, orange, and red layers, adding frosting between each.
Frost the top and sides of the cake with a thin crumb coat. Chill for 15-30 minutes.
Apply a final, smooth layer of frosting. Decorate with sprinkles and edible glitter if desired.
Slice to reveal the vibrant rainbow layers and serve at room temperature. This cake pairs beautifully with a glass of milk or a scoop of vanilla ice cream. 🎉
