Preheat a fan forced oven to 120C / 250F (140C / 285F for no fan). Line two cupcake trays with white cupcake liners. Set aside.
Whisk wet ingredients together - Add the buttermilk, oil, eggs, vanilla extract, red liquid food dye and white vinegar to a jug or bowl and whisk until well combined.
Combine dry ingredients - To a large mixing bowl, add the cake flour, cocoa powder, baking powder, bicarb soda, salt and caster sugar. Whisk to combine.
Add wet ingredients - add the wet ingredients to the dry ingredients and whisk only until no dry ingredients are showing. Scrape down the bowl at least once to make sure it’s combined well. Take care not to overmix otherwise you’ll end up with tough cupcakes.
Scoop into cupcake liners - Fill your cupcake liners up 3/4 of the way. Using an ice-cream scoop to transfer the batter to the cupcake liners makes this a quick and easy process, and ensures each liner contains the same amount of batter and that the cupcakes will bake evenly.
Bake - Bake for 40 minutes, or until a toothpick inserted in a cupcake comes out clean. The cupcakes will look shiny and moist on top when they’re ready. If they bounce and don’t sink when you touch them, they’re done. Once baked, allow to cool completely.
Serving suggestion - These cupcakes are perfectly paired with my cream cheese frosting recipe, but are also nice with chocolate buttercream.