Preheat the oven to 350°F (175°C). Grease and flour a baking pan.
In a bowl, mix melted butter and sugar until smooth. Add eggs one at a time, mixing well after each. Stir in flour and cocoa powder until combined.
Pour half the brownie mixture into the prepared pan. Drop spoonfuls of cream cheese on top, then cover with remaining brownie mixture. Swirl lightly with a knife.
Bake for 30 minutes or until a toothpick inserted in the center comes out with a few moist crumbs. Cool before serving.
Notes
For a fudgier brownie, reduce flour by 1/4 cup and increase cocoa to 3/4 cup.