Preheat the oven to 350°F (180°C) and spray two 9-inch cake pans with non-stick spray and line the bottoms with circles of parchment paper.
Sift the gluten free flour and cocoa powder into a mixing bowl and add the white sugar, baking soda, baking powder, salt and instant espresso powder and mix together.
Prepare the vegan buttermilk by adding 1 Tbsp lemon juice to a measuring jug and adding soy milk up to the 1 cup (240ml) line. Let it curdle.
Prepare the flax eggs by adding 2 Tbsp of ground flaxseed meal to a bowl and then adding 6 Tbsp hot water. Let it sit for a minute to become gloopy.
Add the vegan buttermilk to the mixing bowl along with the flax eggs, oil and vanilla extract. Stir into a thick batter.
Add the hot water and whisk it in. The batter will be thin.
Divide the batter evenly between the two prepared 9-inch cake pans.
Bake for 30 minutes or until a toothpick inserted into the center of one of the cakes comes out clean.
Allow to cool in the cake pans for a few minutes before transferring them to wire cooling racks to cool completely before frosting.
Frost with whipped vegan chocolate ganache or vegan chocolate buttercream frosting.