Preheat the oven to 350°F (180°C) and prepare two 9-inch cake pans by spraying with non-stick spray and lining the bottoms with circles of parchment paper.
Sift the flour and cocoa powder into a mixing bowl and add the sugar, baking soda, baking powder, salt and instant espresso powder.
Mix the homemade buttermilk by adding 1 Tablespoon of lemon juice to a measuring jug and then adding room temperature milk up to the 1 cup (240ml) line and letting it curdle into buttermilk.
Add the buttermilk, canola oil, eggs and vanilla to the dry ingredients and stir it into a thick batter.
Add the hot water and use a hand whisk to whisk it into the batter. You will now have a thin batter and this is perfect.
Divide the batter evenly between the two prepared cake pans and bake for 30 minutes or until a toothpick inserted into the center of one of the cakes comes out clean.
Let the cakes cool in the pans for a few minutes before transferring them to wire cooling racks to cool completely before frosting.