01 - Preheat oven to 350°F. Line an 8x8 inch baking pan with parchment paper, allowing overhang for easy removal.
02 - Whisk melted butter and sugar in a large bowl until smooth. Add eggs, vanilla extract, and red food coloring; whisk until fully combined.
03 - Sift flour, cocoa powder, and salt into the wet mixture. Fold gently with a spatula until just combined; avoid overmixing.
04 - Reserve 1/4 cup of red velvet batter. Spread remaining batter evenly in prepared pan.
05 - Beat cream cheese with sugar until smooth. Add egg and vanilla extract; mix until creamy and well incorporated.
06 - Pour cheesecake mixture over brownie batter in pan; spread evenly to cover surface.
07 - Drop spoonfuls of reserved red velvet batter onto cheesecake layer. Use knife or skewer to gently swirl batters together for marbled pattern.
08 - Bake for 33-36 minutes until center is just set and toothpick inserted comes out with few moist crumbs.
09 - Cool completely in pan on wire rack before lifting out and cutting into squares.