Preheat the oven to 350°F (175°C).
Grease and flour your cake pans.
In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.
Add eggs one at a time, beating well after each addition.
Stir in the Kahlua and vanilla extract until well combined.
In another bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, alternating with buttermilk.
Mix until just combined; do not overmix.
Pour the batter evenly into the prepared pans and smooth the tops.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
Let the cakes cool in the pans for 10 minutes before transferring to a wire rack.
Dust with powdered sugar before serving, if desired.