Preheat the oven to 175°C / 350°F. Line a 23x23 cm (9x9 in) pan with parchment paper, allowing overhang for easy removal.
Mix graham cracker crumbs with melted butter until evenly moistened. Press the mixture firmly into the pan to form a crust. Bake for 8 minutes, then cool slightly.
In a large bowl, beat cream cheese and sugars until smooth. Add eggs one at a time, mixing gently. Incorporate sour cream, vanilla, flour, and salt until combined.
Spoon half the cheesecake batter over the crust, then scatter half the diced apples over it. Drizzle half the caramel sauce, gently swirled. Repeat with remaining batter, apples, and caramel.
Bake for 40–45 minutes until the center is set but still slightly wobbly. Cool to room temperature, then refrigerate for at least 3 hours before slicing.
Just before serving, drizzle with extra caramel and a sprinkle of cinnamon if desired.