Using cupcake liners, line a cupcake pan and preheat the oven to 350 degrees.
Mix the butter, oil, buttermilk, eggs, vanilla, and vinegar in a mixer with a paddle attachment. There may be lumps in the mix.
In a separate bowl, sift the flour, cocoa powder, salt, and baking soda. Slowly add the dry ingredients to the wet ingredients while the mixer is on low speed. Mix until smooth and there are no more lumps, but don’t mix too much.
Stir the food colouring according to your preferences. As a result of the cocoa powder, the cupcakes will be dusty red in colour. So you can omit the cocoa powder if you want bright red cupcakes.
Fill the liners about two-thirds of the way. For mini muffins, bake for 11 minutes and turn the cupcakes over halfway through. For regular-sized muffins, bake for about 20 minutes, turning them over halfway through. Put a toothpick into the cupcakes to see if they’re done. If the toothpick comes out clean, the cupcakes are done.