Preheat your oven to 350°F (175°C). Melt the unsalted butter in a medium saucepan over low heat. Stir in the granulated sugar, allow to cool, then mix in eggs and vanilla extract.
Sift together all-purpose flour, cocoa powder, and salt. Gradually blend into the cooled butter mixture, stirring until smooth.
Pour the brownie batter into a greased 9-inch springform pan and bake for 25-30 minutes until a toothpick comes out with a few moist crumbs. Allow to cool.
In a large bowl, beat cream cheese and sugar with an electric mixer. Add eggs, vanilla extract, and sour cream; mix until smooth.
Pour the cheesecake mixture over the cooled brownie base and bake for an additional 30-35 minutes until slightly jiggly in the center.
For the caramel sauce, melt sugar in a saucepan until deep amber. Stir in butter and cream, then add sea salt to achieve a smooth sauce.
Drizzle warm caramel sauce over the cheesecake once it has cooled to room temperature, then refrigerate for at least 2 hours to set.
Notes
Use room temperature ingredients for best results. Chill thoroughly before serving to enhance flavors.