Preheat the oven to 350°
Prepare your baking pan iwth a pan release on the bottom and 1 inch up on the sides.
In the bowl of a mixer add the cake mix, flour, sugar, sour cream, milk, vinegar, cocoa, red food coloring, salt, baking soda, vanilla, oil, butter, and eggs.
Mix on low until all ingredients are combined, then mix on medium speed for 2 minutes. Stop the mixer and scrape the sides and bottom of the mixing bowl to be sure all ingredients will get well mixed. Mix on medium speed for 2 more minutes.
Pour cake batter into the prepared pan. Spread smooth.
Bake for 55-60 minutes, then begin testing for doneness. When a toothpick comes out cream. This is a large cake be patient. Test every 2 minutes.,
Allow the cake to cool completely, this will take about an hour. Place the cake in the fridge once completely cooled if you prefer a more dense cake. If frosting the next day, cover the cake and leave on the counter, or cover it with plastic wrap and foil and place the in the refrigerator or freeze.
The cream cheese frosting recipe is in the post below this recipe. Other great options are chocolate frosting, buttercream frosting, swiss meringue frosting, or try Italian meringue frosting. I have lots of frosting recipes on my website.