Preheat the oven to 350°F/175°C. Line and grease three eight-inch cake pans, or four, seven-inch pans.
Combine 2 cups all-purpose flour, 2 cups sugar, 3/4 cup baking cocoa, 2 tsp baking powder, 1 1/2 tsp baking soda, and 1 tsp of salt in a large bowl. Whisk together until combined.
In a separate, large bowl, add 1 cup of hot water and 2 tsp instant espresso or coffee. Stir until dissolved.
Add in 1 cup buttermilk, 1/2 cup oil, 2 eggs and 2 tsp vanilla extract into the instant espresso mixture. Give the mixture a quick stir to combine the ingredients.
Pour the wet ingredients into the dry ingredients. Mix by hand until fully incorporated. The batter will be on the thin side, but that’s the consistency you're after!
Divide the batter evenly between the cake pans, and bake for about 23-25 minutes. I like to use a kitchen scale to weigh the pans. It makes sure each pan has the exact same amount of batter and helps the cake layers bake up to be the same height.
Remove the cake layers from the oven and let them cool in the pans for about 10 minutes. Gently run an offset spatula around the rim of the cake pans to loosen them, then flip them onto wire racks to finish cooling.
Once cooled, use a serrated knife to level the top of each cake layer. If you make these in advance, wrap and freeze them at this point.