Grease two 8 inch round cake pans. To make sure the came comes out easily, cut a round piece of parchment paper and grease it to the bottom of the cake pan.
In an electric mixer, beat the butter and sugar until whipped. Add in the eggs one at a time and continue to beat on medium.
Turn the mixer to low and add in sour cream and vanilla extract.
Alternate the flour mixture with the buttermilk while the mixer is on low.
Using a spatula, scrape the bottom and sides of the mixer to incorporate all of the ingredients.
Divide and pour the batter into both pans evenly.
Bake in a preheated 350-degree oven for 25-30 minutes.
Let the cakes cool and then remove them from the pan.
Cut off the top part of the cake that has risen in the center to give yourself a flat surface to stack them
While the cakes are cooling, whip up a batch of our chocolate buttercream frosting.
Place one layer of cake on a cake stand or marble platter and add a giant dollop of buttercream over the top.
Spread it out evenly and then add the second layer of cake over the top.
Add another dollop of chocolate frosting over the top and spread out evenly.
Save about 1/4 cup frosting to do the star pattern around the edge.
Start frosting the sides of the cake until it’s all covered.
Wipe the bottom of the cake stand to remove any chocolate frosting around the edges.
Using a star tip and a piping bag, fill the bag with chocolate frosting and then pipe around the edge of the cake.
Add rainbow sprinkles over the cake!