1/2 cup butter, softened
1-1/2 cups sugar
2 eggs, room temperature
1 teaspoon vanilla extract
2 teaspoons royal blue food coloring
1-2 drops violet food coloring
2-1/4 cups all-purpose flour
1 teaspoon baking soda
1/2 teaspoon baking powder
1-1/2 tablespoons cocoa powder
1/2 teaspoon salt
1-1/3 cups buttermilk, room temperature
1 tablespoon white vinegar
Frosting:
2 (8-ounce) packages cream cheese, softened
1/2 cup butter, softened
6 cups powdered sugar
2 tablespoons milk
1 teaspoon vanilla extract
Step 1: Cream the butter and sugar
Preheat the oven to 350°F. In another small bowl, combine the buttermilk and vinegar and set aside. Grease two 8-in. round cake pans. In the bowl of a stand mixer fitted with the paddle attachment, or a mixing bowl with a hand mixer, cream the softened butter and sugar until light and fluffy, about five minutes. Mix in the eggs and mix in the vanilla extract.
Step 2: Add the food coloring
Mix in the blue food coloring, along with the violet food coloring. Mix thoroughly to incorporate the color, and adjust as needed.
Step 3: Add the dry ingredients
In a small bowl, whisk the dry ingredients to combine. Gradually mix the dry ingredients into the butter mixture, alternating with the buttermilk. Mix until just combined. Add additional food coloring if necessary.
Step 4: Bake the cakes
Divide the batter evenly between the two prepared cake pans. Bake the cakes for 24 to 26 minutes until they’re set and a toothpick inserted into the center comes out clean. Once baked, remove the cakes from the oven and set them aside to fully cool.
Step 5: Make the cream cheese frosting
In a mixing bowl, cream together the cream cheese and butter. Mix in two cups of powdered sugar, milk and vanilla extract. Gradually mix in the remaining powdered sugar until the mixture comes together. Turn the speed up on the mixer to whip the frosting until smooth.
Step 6: Assemble the cake
Place one cake layer on a cake stand. Top the layer with a generous amount of frosting, and place the second cake layer on top. Frost the exterior of the cake using a piping bag or offset spatula.