In a large bowl, whisk your flour, sugar, cocoa powder, salt, and baking powder. Set aside.
In another bowl, combine your eggs, vegetable oil, milk (2 Tbsp.), vanilla, white vinegar, and red food coloring.
Stir in your wet ingredients in with your dry ingredients. Stir until completely combined. It will be thick.
Remove a 3/4 cup of the brownie mixture and set aside in another bowl. Whisk in the rest of your milk (3 Tbsp.).
Pour your brownie mixture into the jelly roll pan. Smooth out the batter to the edges of the pan.