Preheat your oven to 160°C (320°F). Grease an 8 x 8-inch baking pan and line it with baking paper.

Crush the digestive biscuits until they resemble damp sand. Combine with melted butter and press into the pan to form the crust. Chill for about 15 minutes.

Beat cream cheese until smooth; add sugar, salt, and vanilla extract. Incorporate eggs one at a time.

Chop apples and mix with sugar, lemon zest, cinnamon, and nutmeg. Let sit for 5 minutes.

Mix chilled butter, flour, demerara sugar, and granulated sugar until resembling coarse crumbs.

Pour cheesecake filling over crust, spread the spiced apple mixture evenly, and sprinkle crumble topping.

Bake for 45-50 minutes until topping is golden and cheesecake is slightly jiggles in center. Cool on a wire rack.

Chill in the refrigerator for at least 3 hours, or overnight for best flavor.

Lift bars out using overhanging paper, slice into squares, and drizzle with caramel sauce just before serving.