Preheat your oven to 350°F (175°C) and prepare an 8x8-inch baking pan lined with parchment paper.

In a mixing bowl, combine melted butter with sugar until blended. Whisk in eggs, vanilla, red food coloring, vinegar, and cocoa powder. Fold in flour and salt until just incorporated.

Set aside 1/4 cup of the brownie batter. Pour the remaining batter into the prepared pan and spread evenly.

In another bowl, beat cream cheese until smooth. Gradually add powdered sugar, then the egg, mixing until creamy.

Spread cream cheese mixture over the brownie base. Drop spoonfuls of reserved brownie batter over the cream cheese and swirl with a toothpick.

Bake for 35-40 minutes until a toothpick inserted comes out with a few moist crumbs.

Cool completely at room temperature, then refrigerate for at least 2 hours before cutting.