Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a large mixing bowl, cream together the softened butter and sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

In another bowl, combine the flour, cocoa powder, baking powder, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, and mix until just combined.

Divide the batter evenly between the prepared cake pans.

Bake in the preheated oven for 30 minutes or until a toothpick inserted in the center comes out clean.

Allow the cakes to cool in the pans for 10 minutes, then transfer to a cooling rack to cool completely.

In a mixing bowl, beat the softened butter until creamy.

Gradually add the powdered sugar and cocoa powder, mixing until well combined.

Add the milk and vanilla extract, and beat until the frosting is smooth and fluffy.

Once the cakes are completely cool, place one layer on a serving plate.

Spread a layer of frosting on top of the first cake layer.

Place the second cake layer on top and frost the top and sides of the cake with the remaining frosting.

Slice and serve the cake. Enjoy!