Preheat the oven to 350°F. Grease and flour two 9-inch cake pans. Set up cooling racks.
In a small bowl, whisk together 1 cup of milk and 1 tablespoon white vinegar. Set aside. The milk will curdle slightly as it sits; this is normal.
In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking powder, and salt.
Pour in the milk/vinegar mixture, remaining 1 cup milk, oil, vanilla extract, and food coloring. Using an electric mixture at low speed, mix for 1 minute, just until combined.
In a small bowl, whisk together the remaining 1 tablespoon white vinegar and baking soda. Add to the batter and continue mixing just until incorporated, about 30 seconds. Pour batter evenly into the prepared baking pans.
Bake for 35 minutes. Allow to cool in the pans for 10 minutes then turn out onto cooling racks to finish cooling completely then prepare the frosting.