Preheat oven to 350F (175C) and spray two 8” cake pans (see note for using different sized pans) with baking spray and line the bottoms with parchment paper. Set aside.

Combine milk and food coloring in a large measuring cup or small bowl, whisk to thoroughly combine and set aside.

In a large bowl, whisk together flour, granulated sugar, brown sugar, cocoa powder, baking soda, and salt until thoroughly combined.

Add melted butter and oil and stir until all ingredients are well-combined and no longer dry (the mixture will be thick).

Add eggs and egg yolk, one at a time, stirring until very well-combined after each addition. Pause occasionally to scrape the sides and bottom of the bowl with a spatula.

Stir in vanilla extract and vinegar then gradually add milk mixture and stir very well until completely combined and batter is entirely smooth and lump-free. While it's not impossible to over-mix this cake batter, it is difficult to do so and you are more likely to accidentally under-mix, so stir well!

Evenly divide batter into prepared pans and bake on center rack on 350F (175C) for 40-45 minutes or until a toothpick inserted in the center comes out with a few moist crumbs (preferred) or clean (once the toothpick comes out clean it is nearing becoming over-baked, take it out of the oven at once).

Allow cakes to cool in their pans for 10-15 minutes, then run a knife along the inside rim to loosen the cakes and carefully invert onto a cooling rack to cool completely before covering with frosting. My cakes generally bake up nice and flat, but if yours are domed, level with a sharp serrated knife after cooling and before stacking and frosting.