Preheat oven to 350°F.
In a medium bowl, whisk together egg, vanilla and melted butter. Add in sugar and stir to combine.
Add flour, cocoa powder, salt and baking powder and stir to combine and incorporate completely. Mixture will be smooth but may have some very small lumps.
Scoop out 1/3 cup of the brownie batter and set aside. Pour the rest of the brownie batter into a well greased, or parchment lined 9x9in pan and spread evenly (8x8in. will work as well, and set aside.
In a separate bowl, using an electric mixer, beat cream cheese and sugar until smooth and creamy. Add in egg and vanilla and beat until fully incorporated. Add dulce de leche and stir in slowly. I like to do it this way to allow some caramel like streaks to still be visible. You can fully incorporate it if you would like.
Pour the cheesecake mixture on top of the brownie batter and spread evenly. Take the reserved brownie batter and drop in dollops across the cheesecake. Take a knife or long toothpick and swirl the two together.
Bake for about 22-25 minutes or until a toothpick comes up mostly clean (you don't want a brownie over baked, so I don't like mine coming up completely dry.)
Serve with extra dulce de leche drizzle and a big scoop of ice cream!