Preheat the oven to 325°F. Grease a 9-inch springform pan.
In a medium bowl, whisk together granulated sugar, cocoa powder, flour, salt, and baking powder. Add melted butter, eggs, and vanilla extract. Mix until well combined.
Pour half of the brownie batter into the prepared springform pan, spreading it evenly.
In another bowl, beat the softened cream cheese with powdered sugar and vanilla extract until smooth. Add the egg and mix until just combined.
Pour the cream cheese mixture over the brownie layer in the pan.
Top with the remaining brownie batter, spreading it gently over the cream cheese layer.
Bake for 45-50 minutes, or until the edges are set and the center is slightly jiggly.
Remove from the oven and let cool in the pan for about 15 minutes. Run a knife around the edge to loosen, then remove the sides of the springform pan.
Chill in the refrigerator for at least 2 hours before serving.