Preheat your oven to 350°F (175°C) and line a 12-cup muffin tin with cupcake liners.
Whisk together dry ingredients: In a medium bowl, sift together the flour, sugar, cocoa powder, baking soda, and salt. Set aside.
Mix the wet ingredients: In a large bowl, whisk the egg, vegetable oil, buttermilk, red food coloring, vanilla extract, and vinegar together until smooth.
Combine the wet and dry ingredients: Gradually add the dry ingredients to the wet ingredients and mix until just combined. Be careful not to overmix.
Fill the cupcake liners: Spoon the batter evenly into the cupcake liners, filling each about 2/3 full.
Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Cool the cupcakes in the pan for 5 minutes, then transfer them to a wire rack to cool completely before frosting.
