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, and red food coloring; whisk thoroughly.
03 - Sift flour, cocoa powder, and salt into the bowl. Gently fold with a spatula until just combined—avoid overmixing.
04 - Reserve ¼ cup of brownie batter. Spread remaining batter evenly in the prepared pan.
05 - Beat cream cheese until smooth. Add sugar, egg yolk, and vanilla; beat until creamy and fully blended.
06 - Drop cheesecake mixture over the brownie batter. Dollop reserved brownie batter on top. Use a knife to swirl gently for a marbled effect.
07 - Bake for 32–35 minutes until the center is just set. A toothpick should emerge with a few moist crumbs.
08 - Cool completely in the pan on a wire rack. Lift using parchment, cut into squares, and serve.