Preheat oven to 350°F. Line a regular sized cupcake pan with cupcake liners and set aside.
In the bowl of a stand mixer whisk the cake flour, sugar, cocoa powder, baking soda, and salt.
In a separate bowl, or large liquid measuring cup, whisk the vegetable oil, sour cream, buttermilk, egg, vanilla extract, white vinegar, and black food coloring.
Add the wet ingredients to the dry ingredients (using a paddle attachment) and mix on low until ingredients are combined.
Portion the batter into the cupcake liners until ½ full (I use a size 20, 3 tablespoon sized cookie scoop to portion my batter evenly amongst the cupcake compartments). Bake for 15-18 minutes or until a toothpick comes out clean from the center of the cupcakes.
Remove and transfer the cupcakes to a wire rack to cool completely.
Black Frosting
Beat the butter and cream cheese in a stand mixer until smooth and creamy about 2-3 minutes. Add the powdered sugar ½ cup at a time. Mix in the black cocoa powder, vanilla extract and black gel coloring, about 2-3 drops. Whip until smooth. Add a splash of heavy cream if needed, to get desired consistency.
Frost the cooled cupcakes and add sprinkles if you’d like. Store frosted cupcakes covered in the fridge.
Notes
Cake flour: If you don't have cake flour you can make a homemade cake flour substitute by measuring 1 cup of all purpose flour, removing 2 tablespoons of all purpose flour (so you now have 14 tablespoons of all purpose flour) and adding 2 tablespoons of cornstarch. Sift this mixture together (sifting helps combine and aerate the flour so that its similar to cake flour). Then measure the amount of cake flour you need. Black cocoa powder: is a dutch processed cocoa powder. The black cocoa powder has a distinct flavor, its much deeper and I LOVE it! If you want to experience true black velvet cupcakes, use black cocoa powder. I highly encourage you to do so! If you don’t want to buy it you can use a dutch process cocoa powder or natural cocoa powder (dark or regular) and add gel black food coloring to the batter. The batter won’t be as dark, but will get it closer. And note, the taste won't be the same. Cream cheese should be the block cream cheese and not the cream cheese spread.Frosting tip: You can make the frosting in advance and store it in the fridge. Making the black frosting in advance also allows the color to deepen slightly. Frosting can be stored in the fridge for up to 3 days. Let it sit in the fridge, covered. When ready to use remove from the fridge and let it come back to room temperature. Using a rubber spatula give it a good stir from side to side for a few minutes or place it back in the bowl of your stand mixer and beat until smooth.Storing: Cupcakes can be stored in the fridge, covered (so they don't dry out), for up to 1 week. Frosted cupcakes will last about 3 days.