1. Preheat the oven to 350°F (175°C) and line a 9×9-inch baking pan with parchment paper, leaving an overhang.

2. Mix graham cracker crumbs, granulated sugar, melted butter, and salt until combined, then press into the pan and bake for 8 to 10 minutes.

3. In a bowl, beat cream cheese and sugar until smooth, then add eggs one at a time, flour, sour cream, and vanilla bean paste, mixing until just combined.

4. Toss apple slices with brown sugar, cinnamon, nutmeg, and lemon juice, then spread evenly over the cooled crust.

5. Pour the cheesecake filling over the apples and spread gently to the edges.

6. Combine oats, brown sugar, flour, cinnamon, and cold butter, work into coarse crumbs, and sprinkle over the filling.

7. Bake for 40 to 45 minutes until the center is set and the topping is golden, then cool at room temperature for one hour and refrigerate for at least four hours.

8. Lift the bars using the parchment overhang and slice into squares with a sharp knife, wiping the knife between cuts.