Butter a 20cm square brownie tin and line with baking parchment. Heat the oven to 180C/160C fan/gas 4. Whisk the melted butter and sugar with the vanilla extract in a bowl. Once combined, whisk in the food colouring and eggs until the mixture is a vibrant red.

Sift in the cocoa powder and flour, and add the vinegar. Fold together using a spatula. For the cheesecake swirl, mix the soft cheese, egg yolk and sugar together, and set aside.

Pour most of the brownie batter into the tin and dollop in the cheesecake mixture. Pour the rest of the brownie batter on top and use a skewer to lightly swirl the two together. Bake for 30 mins until shiny on top. Remove from the oven and cool in the tin for 30 mins, then remove to a wire rack and cool completely. Slice into 16. Will keep in an airtight tin for five days, or frozen for up to a month.