In the mixer's bowl, mix together at low speed the 18oz flour, 24oz granulated sugar, 3oz cornstarch, 2oz unsweetened cocoa powder, 1 tbsp baking soda, 1-1/2 tsp baking powder, and 1-1/2 tsp salt
Add 4 large eggs, 1-1/2 cups buttermilk, the warm water, 1/2 cup of vegetable oil, 1 tsp of vanilla extract, 1 tsp of white vinegar, and 2 tbsp of red food coloring
Mix on medium for a couple of minutes until the mixture is smooth
Pour the batter evenly among the three cake rounds
Bake at 350°F for about 30 minutes, until a toothpick stuck in the center of the cakes comes out clean
Let the cakes cool in the rounds for about 15 minutes
Turn the cakes out onto the rounds and let them cool completely before adding the frosting