Preheat & Prepare: Preheat oven to 325°F (163°C). Grease a 9-inch springform pan and line the bottom with parchment paper.
Make the Brownie Layer: In a bowl, whisk melted butter and sugar. Add eggs and vanilla, mixing well. Stir in cocoa powder, flour, salt, and baking powder until combined. Spread evenly in the pan. Bake for 15 minutes, then set aside to cool slightly.
Make the Cheesecake Layer: In a separate bowl, beat cream cheese and sugar until smooth. Add eggs one at a time, mixing until fully incorporated. Stir in vanilla extract.
Assemble & Bake: Pour the cheesecake batter over the brownie layer. Bake for 35-40 minutes, or until the center is set but slightly jiggly. Let cool at room temperature, then refrigerate for at least 4 hours or overnight.
Add Caramel Topping: Drizzle caramel sauce over the chilled cheesecake before serving. Sprinkle with sea salt if desired.