Assemble the necessary ingredients.
To ensure even baking, position two racks in the upper and lower thirds of the oven. Preheat to 350°F, then prepare two 9-inch round cake pans by greasing and flouring them. Set these pans aside for later.
When making cakes, start by creaming butter and sugar in a large bowl until it becomes light and fluffy.
Gradually add the eggs, one at a time, and make sure to beat the mixture well after each addition.
Combine vinegar, royal blue and violet food coloring, and vanilla extract.
Combine cake flour, cocoa powder, baking soda, and salt in another medium-sized bowl.
Incorporate the dry ingredients into the creamed mixture in batches, while alternating with buttermilk. Be sure to beat the mixture thoroughly after each addition.
Divide the mixture equally between the baking pans. While baking, rotate the pans halfway through the cooking time. Check with a toothpick; it should come out clean. The total baking time is 20 to 25 minutes.
After baking, let the cake layers cool for 10 minutes, then transfer them to wire racks for complete cooling.
Creating frosting is easy. Just blend confectioners' sugar, butter, cream cheese, and vanilla in a large bowl until it's smooth and creamy.
Start by positioning the first cooled cake layer on the serving platter or cake stand, then proceed to frost the layer.
To assemble, position the second cake layer on top, apply frosting to the top and sides, and then refrigerate until it's time to enjoy.