Preheat the oven to 350℉. Spray three 8 inch cake pans with non stick baking spray. Line the bottom with parchment paper and spray again. Set aside.
In a medium sized bowl, sift together flour, cocoa powder, cornstarch, baking soda, baking powder, and salt. Set aside.
2 cups All-purpose flour, 1 cup Unsweetened cocoa powder, 1/4 cup Cornstarch, 2 tsp Baking powder, 1 tsp Baking soda, 1 tsp Salt
In a saucepan, heat water until hot and steaming.
1 cup Hot water
In a mixing bowl, combine buttermilk, oil, vanilla, eggs, and sugar. Once it is all combined, slowly add in the hot water. Go slowly so you don't cook the eggs.
1 cup Oil, 1 tsp Pure vanilla extract, 1 cup Buttermilk, 4 Large eggs, 1 3/4 cups White granulated sugar
Add in the dry ingredients and mix until combined.
Pour the cake batter into three pans evenly. Bake for 23-26 minutes. The cake is done baking when a toothpick inserted comes out clean.
Let the cakes sit in the pans for 10 minutes before transferring to a cooling rack. Allow the cakes to cool completely before decorating.