Preheat oven to 350 degrees. Grease two 9” cake pans.
In a medium bowl, whisk together the flour, cocoa, salt and baking powder.
In another medium bowl, whisk together the milk, beet puree, orange juice and vinegar.
In the bowl of your stand mixer, cream together the butter, sugar, and vanilla. Add the eggs one at a time, beating well after each addition. Add a third of the liquid ingredients, followed by a third of the dry ingredients, alternating wet and dry and mixing well after each addition.
Pour into your prepared pans and bake for 30 minutes, or until a toothpick comes out clean and the tops look firm. Let cool in the pans for 10 minutes, then remove from pans and cool completely on a wire rack before frosting.
To frost this recipe for Red Velvet cake, I recommend spreading on a thin crumb coat, then placing the cake in the fridge for an hour to let it harden a bit. Remove cake from the fridge and continue frosting. This will prevent red crumbs from mixing with the white frosting.