Preheat your oven to 350°F (175°C). Grease two round cake pans and dust with flour.
In a bowl, whisk together the flour, cocoa powder, baking powder, and salt.
In a large mixing bowl, cream the butter and sugar until fluffy (about 3 minutes).
Add the eggs one at a time, mixing well after each addition. Stir in vanilla extract.
Gradually mix in the dry ingredients alternating with buttermilk until just combined.
Divide the batter between prepared pans and bake for 25-30 minutes or until a toothpick comes out clean. Let cool completely before frosting.