Preheat the oven to 175°C (350°F). Line a 23×23 cm (9×9 inch) baking pan with parchment paper, leaving an overhang for easy removal

In a bowl, combine graham cracker crumbs, granulated sugar, melted butter, and ground cinnamon; press evenly into the bottom of the prepared pan to form the crust

Bake the crust for 8–10 minutes until set and lightly golden; set aside to cool

In a skillet over medium heat, melt 15 g butter; add diced apples, brown sugar, ground cinnamon, and nutmeg; sauté until apples are tender and caramelized, about 6–8 minutes; set aside to cool slightly

In a large mixing bowl, beat cream cheese and granulated sugar until smooth and creamy

Add the egg, vanilla extract, and flour to the cream cheese mixture; beat until fully combined and silky

Spoon half of the cheesecake batter over the baked crust and spread gently

Scatter the cooked apple mixture evenly over the cheesecake layer

Drop spoonfuls of the remaining cheesecake batter over the apples and gently swirl with a knife to create marbling

Bake the bars for 30–35 minutes or until the center is set and edges are lightly golden

Remove from oven and let the bars cool completely at room temperature, then refrigerate for at least 2 hours

Drizzle caramel sauce over the chilled bars before slicing; sprinkle with flaky sea salt if desired