Preheat oven to 325°F (160°C). Grease a 9-inch springform pan with butter or nonstick spray. Line the bottom with parchment paper if desired.
Prepare the brownie layer. If using a box mix: follow package instructions. If homemade: whisk together butter and sugar, add eggs, then stir in cocoa powder, flour, baking powder, and salt. Pour batter into the pan and bake for about 20 minutes until the top is set but still soft. Remove from oven.
Make the cheesecake filling: Beat cream cheese and sugar until smooth. Add eggs one at a time, mixing slowly. Blend in sour cream and vanilla until silky.
Pour cheesecake mixture over brownie base. Tap gently to remove air bubbles. Bake for 40–45 minutes until the center is set but slightly jiggly.
Turn off oven, crack the door, and let cheesecake cool inside for 1 hour.
Refrigerate for at least 4 hours or overnight.
Drizzle with caramel sauce and sprinkle pecans before slicing with a hot knife.
