Preheat the oven to 350°F. Grease and line two 9-inch round cake pans with parchment paper.
In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt.
In a separate bowl, whisk together the buttermilk, oil, eggs, and vanilla extract.
Add the wet ingredients to the dry ingredients and mix until combined.
Slowly pour in the hot coffee while stirring. The batter will thin.
Divide the batter evenly between the prepared cake pans.
Bake for 28-32 minutes, or until a toothpick inserted in the center comes out clean.
Allow the cakes to cool in the pans for 15 minutes before transferring them to a wire rack to cool completely.
To make the frosting, beat the softened butter until smooth. Add the cocoa powder and mix until incorporated.
Gradually add the powdered sugar, followed by the heavy cream, vanilla extract, and salt. Beat until light and fluffy.
Place one cake layer on a cake stand or serving plate. Spread an even layer of frosting on top.
Add the second cake layer and frost the top and sides of the cake.
Slice and serve.
