- Preheat your oven to 175°C (350°F) and line a 12-hole cupcake tin with paper cases.
- Whisk together the flour, cocoa powder, baking powder, baking soda, and salt in a bowl and set aside.
- Beat the softened butter and caster sugar together with an electric mixer on medium-high speed until pale and fluffy, about 3–4 minutes, then add the eggs one at a time, mixing well after each addition.
- Mix the buttermilk, red food colouring gel, vanilla extract, and white wine vinegar together in a jug, then alternately fold the dry ingredients and the buttermilk mixture into the butter mixture in three additions, starting and ending with the dry ingredients.
- Divide the batter evenly among the cupcake cases, filling each about two-thirds full, then bake for 18–20 minutes until a skewer inserted in the centre comes out clean. Allow to cool completely on a wire rack.
- Make the cream cheese frosting by beating the softened butter until smooth, then add the cream cheese and beat until combined. Gradually sift in the icing sugar and beat on low then high speed until thick, smooth, and fluffy.
- Transfer the frosting to a piping bag fitted with a large star nozzle and pipe generous swirls onto each cooled cupcake.
Tip: Ensure both the butter and cream cheese for the frosting are at true room temperature before beating — cold cream cheese will leave lumps, and overly warm butter will make the frosting too loose to hold its piped shape.