Preheat the oven to 350F (180C). Line a muffin tin with 6-7 muffin papers using the middle 6 cavities of the muffin tin.
In a large bowl, whisk together the flour, cocoa, sugar, baking soda and salt. If the cocoa has lumps, sift it into the bowl.
In a separate bowl, whisk together the oil, melted butter, egg, vanilla extract, buttermilk, red food coloring and vinegar.
Make a well in the middle of dry ingredients. Then pour the wet ingredients into the well.
Whisk together until smooth and lump free. Stop whisking as soon as the batter is smooth.
Spoon the batter into the lined muffin tin, filling each about ⅔ to ¾ full. You should end up with 6-7 in total.
Bake in the preheated oven for 15-17 minutes, or until an inserted toothpick comes out clean.
Cool in the pan for at least 10 minutes, then continue to cool the cupcakes on a cooling rack.