Preheat oven to 350°F.
Line two 8-inch round pans with parchment and spray lightly.
Whisk sugar, flour, cocoa, baking powder, baking soda, and salt.
Mix in eggs, buttermilk, oil, and vanilla.
Slowly stir in hot coffee. The batter will be thin.
Pour into pans and bake 30 to 35 minutes, until a toothpick comes out clean.
Cool completely.
For the frosting, mix melted butter and cocoa, then beat in powdered sugar, milk, and vanilla until smooth and fluffy.
Layer, frost, and slice.
For a 9x13 cake, bake 35 to 40 minutes.
