Preheat your oven to 180°C (350°F) and prepare three 8-inch round baking pans. Generously coat the pans with cooking spray and line with parchment paper.

In a large mixing bowl, combine the all-purpose flour, Dutch-process cocoa powder, baking powder, baking soda, kosher salt, and granulated sugar. Whisk together until well blended.

Add in the eggs, buttermilk, vegetable oil, and vanilla extract to the dry mixture. Mix gently until slightly combined with some flour streaks remaining.

Pour in the hot coffee while mixing gently until the batter is smooth and lump-free.

Evenly divide the batter among the prepared pans and bake for 25-30 minutes, until a toothpick comes out clean.

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

Beat the unsalted butter until creamy, then gradually add powdered sugar, cocoa powder, heavy cream, and vanilla extract until smooth and fluffy. Fold in the caramel sauce.

Once cooled, assemble the cake by layering with frosting and caramel sauce between each layer. Finish with a layer of frosting on the outside.