Preparing the Brownie Layer:

1. Preheat your oven to 325°F (163°C) and coat a 9-inch springform pan with nonstick cooking spray.
2. In a large mixing bowl, combine melted butter, granulated sugar, cocoa powder, and salt. Stir until well blended and thickened. If the mixture is too warm, let it cool slightly.
3. Add vanilla extract, then mix in eggs one at a time until thoroughly incorporated.
4. Fold in flour just until combined. Spread the batter evenly into the prepared pan.
5. Bake for approximately 15 minutes, until the surface begins to set but isn’t fully baked. Remove from oven and cool to room temperature, then refrigerate until completely chilled.

Preparing the Cheesecake Layer:

1. In an electric mixer bowl, beat cream cheese until smooth (about 1 minute).
2. Add both sugars and heavy cream, beating until the mixture is well combined and smooth. Scrape down the bowl periodically.
3. Add eggs one at a time, mixing just until incorporated after each addition. Stir in vanilla.
4. Pour the cheesecake mixture over the chilled brownie base. Gently tap the pan on the counter to remove any air bubbles.
5. Place the springform pan on a rimmed baking sheet and bake for 55 minutes to 1 hour, until the cheesecake appears set with a slightly dry top. The center should still jiggle slightly.
6. Turn off the oven, crack the door open, and allow the cheesecake to cool inside for 10 minutes.
7. Remove from oven and cool completely at room temperature on a wire rack.

Finishing Touches:

1. Refrigerate the cheesecake until thoroughly chilled (at least 4 hours or overnight).
2. To serve, release from springform pan, transfer to a serving plate, and cut into slices.
3. Drizzle each slice with salted caramel sauce just before serving.