Preheat oven to 350 degrees. Grease and flour two 9-inch baking pans (or line with parchment paper circles) and set aside.

In the bowl of a standing mixer, stir together sugar, flour, cocoa, baking powder, baking soda, and salt. Add eggs, buttermilk, melted butter and vanilla extract and beat for 2 minutes on medium speed. Stir in hot coffee.

Pour batter evenly between the two pans and bake on middle rack of oven for 30 to 35 minutes (mine were done a bit before the 30-minute mark), until toothpick inserted in centre comes out clean. Allow to cool 5 minutes in pans. Run a butter knife around the edges of each cake. Place a wire cooling rack over top of each pan. Wearing oven mitts, use both hands to hold the racks in place while flipping the cakes over onto the racks. Set the racks down and thump on the bottom of the pans until the cakes release. Cool completely before frosting.

To make the frosting, beat butter, cocoa, sugar, and vanilla together with an electric mixer on high until smooth and creamy, 3-4 minutes. Taste and add additional powdered sugar, if desired. If the icing is too thick to spread, add a splash of milk and beat again to incorporate.