Preheat your oven to 350°F (175°C) and butter and line two 8-inch round cake pans with parchment paper.

In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt.

In a separate bowl, mix the buttermilk, vegetable oil, eggs, and vanilla extract until fully combined.

Gradually add the wet mixture to the dry ingredients, stir until just combined, and then whisk in the hot coffee.

Divide the batter equally between the prepared cake pans and bake for about 35 minutes.

Allow the cakes to cool in the pans for 10-15 minutes before inverting onto a cooling rack.

Melt the semisweet chocolate in a heat-proof bowl and allow it to cool slightly.

Beat the unsalted butter until light and pale, then gradually add powdered sugar, a pinch of salt, and vanilla extract.

Fold the cooled chocolate into the butter mixture, followed by the sour cream, and mix until smooth.

Frost the cooled cake layers with the frosting, ensuring an even distribution for a perfect finish.