Preheat your oven to 170°C (340°F) and generously grease the cake tins with butter to prevent the cake from sticking.
In a large mixing bowl, combine flour, baking powder, baking soda, salt, brown sugar, and white sugar. Whisk them together until evenly mixed.
Add the buttermilk, oil, vanilla extract, and eggs, then whisk until the batter is smooth and well blended.
In a separate bowl, mix hot water, cocoa powder, and instant coffee until dissolved. This helps intensify the chocolate flavor. Pour the cocoa mixture into the batter and whisk until completely combined and lump-free.
Divide the batter evenly between the pans and bake for about 20 minutes, or until a toothpick inserted in the center comes out clean.
Once baked, let the cakes cool in their pans before carefully removing them. Level the tops with a sharp knife if needed.