Preheat oven to 325 degrees. Grease and flour a bundt pan (ours had a 12 cup baking capacity- this recipe makes about 7 cups of batter).
Add the first 5 ingredients into the bowl of your mixer. Mix on low speed for at least 30 seconds to combine these dry ingredients (cake flour, sugar, baking powder, cocoa powder, and salt).
Add the softened butter (cut into pieces) to the dry mixture, mixing on low speed just until it looks like coarse sand. The dry ingredients will be moistened/coated by the butter and will stick to together if you press some between two fingers. Don't over-mix or it will turn into a large dough-like ball.
Add the eggs one at a time, mixing until blended.
In a medium sized bowl, combine the sour cream, vegetable oil, milk, red food coloring, vanilla extract, and white vinegar.
With the mixer on lowest speed gradually pour the sour cream mixture into the mixer. Increase the speed to #2 or # 3 (on a KitchenAid mixer). Mix for two minutes. Batter will be smooth and well combined.
Scoop/pour the batter into the prepared bundt cake pan. (If you are using a smaller bundt cake pan, keep in mind that the batter shouldn't exceed ⅔ full so that the cake has room to rise while baking.)
Bake at 325 degrees F for 55 -60 minutes or until an inserted wooden skewer comes out clean or with just a few moist crumbs attached. Baking times may vary and so it is best to peek in as the end time approaches and adjust time as needed.
Allow the freshly baked cake to cool on a wire rack (in the pan) for about 10 minutes before turning out. Allow it to cool completely before adding the frosting.
Makes approximately 7 cups cake batter