Preheat your oven to 350°F (175°C) and line a 9x13 inch baking pan with parchment paper. In a large mixing bowl, cream together the unsalted butter and light brown sugar until light and fluffy. Gradually incorporate the all-purpose flour, ground cinnamon, and salt until the mixture resembles a crumbly dough. Press it evenly into the prepared pan and bake for 8 minutes until slightly golden.

In a large mixing bowl, beat the cream cheese until smooth. Add in sour cream, granulated sugar, and vanilla extract, mixing until fully combined. Add eggs, one at a time, ensuring each is incorporated before adding the next. Gently fold in heavy cream and flour until the mixture is smooth and creamy. Pour over the cooled crust.

In a separate bowl, mix the peeled and diced Granny Smith apples with brown sugar, ground cinnamon, and a dash of nutmeg. Stir until the apples are well coated. Sprinkle the spiced apple mixture evenly over the cheesecake batter.

In another bowl, combine light brown sugar, granulated sugar, all-purpose flour, and old-fashioned oats. Cut in unsalted butter until the mixture becomes crumbly. Sprinkle this streusel topping generously over the apple layer.

Carefully place the pan in the oven and bake at 350°F (175°C) for 20 minutes. Reduce the temperature to 300°F (150°C) and continue baking for an additional 40 minutes, or until the edges are set but the center still jiggles slightly.

Once baked, remove from the oven and let it cool to room temperature in the pan. Cover with plastic wrap and refrigerate for at least 5 hours or, ideally, overnight.

After chilling, take the cheesecake out of the fridge, lift it out of the pan using the parchment paper. Drizzle generously with salted caramel sauce and sprinkle with flaky sea salt. Slice into squares.