Preheat oven to 350°F (175°C). Grease and flour two 9-inch cake pans.
Dry ingredients: In a bowl, whisk flour, sugar, baking soda, salt, and cocoa powder.
Wet ingredients: In another bowl, mix oil, buttermilk, eggs, food coloring, vanilla, and vinegar.
Combine: Gradually add dry ingredients to wet, mixing until smooth (do not overmix).
Bake: Divide batter evenly into pans. Bake for 25–30 minutes or until a toothpick comes out clean.
Cool: Let cakes cool in pans for 10 minutes, then transfer to a wire rack.
Beat cream cheese and butter until smooth.
Add powdered sugar and vanilla, beating until fluffy.
Place one cake layer on a plate, spread frosting, then top with the second layer.
Frost the top and sides. Decorate with sprinkles or crumbs (optional).
