1. Preheat oven to 350°F (175°C) and line a 9×13 inch pan with parchment paper.

2. In a bowl combine graham cracker crumbs, brown sugar, melted butter, and salt, then press into the pan.

3. Bake crust for 8 to 10 minutes until set and lightly golden, then let cool slightly.

4. Beat softened cream cheese and sugar until smooth, then add eggs one at a time, sour cream, and vanilla, mixing gently.

5. Spread cheesecake filling evenly over the cooled crust.

6. Toss diced apples with lemon juice, brown sugar, cinnamon, nutmeg, and cornstarch, then layer over the filling.

7. Combine oats, flour, brown sugar, melted butter, and cinnamon for the topping, then sprinkle over the apples.

8. Bake for 40 to 45 minutes until edges are set and topping is golden, covering with foil if needed.

9. Cool bars in the pan, then refrigerate for at least 3 hours before slicing.

10. Use a sharp knife wiped clean between cuts to slice into bars and serve chilled or at room temperature.