Preheat your oven to 350°F and grease two 8-inch round cake pans.
In a bowl, whisk together flour, baking powder, baking soda, salt, and cocoa powder.
In another bowl, beat butter and sugar until light and fluffy.
Add eggs one at a time, mixing well after each addition.
Add vanilla extract and brewed coffee, then mix in dry ingredients, alternating with sour cream.
Pour the batter evenly into the prepared pans and bake for 25-30 minutes or until a toothpick comes out clean.
Allow the cakes to cool in the pans for 10 minutes, then transfer them to a cooling rack.
While the cakes cool, prepare the mocha buttercream: beat softened butter with powdered sugar until smooth.
Add brewed coffee, cocoa powder, vanilla extract, and a pinch of salt, mixing until light and fluffy.
Once the cakes are cool, spread the buttercream between the layers and on top.
Slice, serve, and enjoy the decadence.