Preheat your oven to 375°F (190°C) and grease an 8x8 inch baking dish.

Melt the unsalted butter in a saucepan over low heat, then remove from heat and stir in sugar, vanilla extract, cocoa powder, salt, red food coloring, and vinegar. Incorporate the eggs one at a time and gently fold in the all-purpose flour.

Pour three-quarters of the brownie batter into the baking dish, spreading it evenly across the bottom.

Beat cream cheese with sugar until smooth, then mix in the egg and a splash of vanilla extract.

Pour the cheesecake mixture over the brownie base and spread it evenly.

Spoon dollops of the reserved brownie batter over the cheesecake layer and swirl gently to create a marbled effect.

Bake for 30-35 minutes until the edges look set and the center has a slight jiggle.

Let the brownies cool in the pan for 1-2 hours, then refrigerate for an hour before slicing.