Preheat your oven to 180°C (350°F) and prepare two 8-inch round baking pans by lining the bottoms with parchment paper and greasing the sides.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, kosher salt, and sifted cocoa powder until well combined.

Add the buttermilk, vegetable oil, pure vanilla extract, and room-temperature eggs to the dry mixture, mixing until just combined.

Gradually stir in the hot coffee until the batter is smooth and free of lumps.

Divide the batter evenly between the prepared baking pans and bake for 25–30 minutes, checking for doneness with a toothpick.

Allow the cakes to cool in the pans for about 10 minutes, then invert onto a wire rack to cool completely.

In a medium saucepan, combine unsalted butter, heavy cream, dark chocolate, cocoa powder, powdered sugar, and a pinch of salt over medium heat, stirring until smooth.

Let the frosting sit at room temperature for about 30 minutes, then refrigerate for 1–2 hours to thicken.

Once the cakes are cool and frosting is thickened, assemble by placing one layer on a serving plate and spreading a dollop of frosting on top before adding the second layer.