Preheat oven to 350°F (175°C) and line a baking pan with parchment paper.
Mix melted butter and sugar until smooth, then beat in eggs and vanilla.
Stir in cocoa powder and red food coloring until combined.
Fold in flour and salt to create brownie batter.
In another bowl, beat cream cheese, sugar, egg, and vanilla until smooth.
Spread most brownie batter into the pan, reserving a few spoonfuls.
Pour cheesecake mixture over brownie layer evenly.
Drop remaining brownie batter on top and swirl gently with a knife.
Bake 25–30 minutes until set in the center.
Cool completely before slicing into squares.
