Preheat your oven to 350°F (175°C). In a medium saucepan over low heat, melt the butter and sugar together, stirring until incorporated. Remove from heat, allow to cool slightly, then whisk in eggs and vanilla until smooth.

In a separate bowl, sift together flour, cocoa powder, and salt. Gradually fold the dry ingredients into the wet mixture until just incorporated. Pour into greased springform pan.

Bake for 25-30 minutes, or until a toothpick comes out slightly moist. Allow to cool completely.

In a large bowl, beat cream cheese until creamy, then add sugar, eggs, vanilla, and sour cream. Mix until smooth.

Pour the cheesecake mixture over the cooled brownie layer and bake for an additional 30-35 minutes, until set but still jiggly in the center. Cool at room temperature for 1 hour, then chill.

To make the caramel, heat sugar in a saucepan, stirring constantly until it melts and turns golden-brown. Stir in butter, cream, and sea salt until smooth.

Drizzle caramel sauce over the cheesecake. Refrigerate for at least 2 hours before serving.