Preheat your oven to 350°F (175°C) and prepare an 8x8-inch baking pan with parchment paper or a light coat of non-stick spray.

In a large bowl, whisk together melted butter and sugar until the mixture is smooth.

Add eggs, vanilla extract, red food coloring, and vinegar to the bowl. Mix well until fully combined.

Sift cocoa powder, flour, and salt into the wet ingredients. Fold gently to form a smooth batter. Reserve 1/4 cup of this batter for later.

In another bowl, beat softened cream cheese with sugar until creamy. Add the egg and vanilla extract and mix until smooth.

Pour the red velvet batter into the prepared baking pan, spreading it evenly.

Dollop the cream cheese mixture on top of the red velvet batter. Use a knife or skewer to swirl the layers together for a marbled effect.

Add small dollops of the reserved red velvet batter on top and incorporate them into the swirl.

Bake for 25–30 minutes, or until the center is set and a toothpick inserted comes out with a few moist crumbs.

Let the brownies cool completely in the pan before slicing and serving. Enjoy!