Preheat oven to 325°F (160°C). In a mixing bowl, combine graham cracker crumbs, sugar, cinnamon, and melted butter until it resembles wet sand. Press firmly into the bottom of a 9-inch springform pan and bake 10 minutes. Let cool while preparing the filling.
Beat cream cheese in a large bowl or stand mixer until smooth and fluffy, about 2–3 minutes. Gradually add sugar, then blend in vanilla. Add eggs one at a time, mixing just until combined. Stir in sour cream and heavy cream until the batter is smooth and velvety.
Pour cheesecake filling over the cooled crust and smooth the top. Wrap the bottom of the pan in foil and place inside a larger baking dish.
Fill the larger dish with hot water halfway up the pan and bake 60–70 minutes until edges are set but center jiggles slightly. Turn off oven, crack door, and let rest 1 hour. Chill in fridge at least 5 hours or overnight.
Melt butter in a skillet over medium heat. Add sliced apples, brown sugar, cinnamon, nutmeg, and lemon juice. Cook 5–7 minutes until apples are tender and caramelized but not mushy. Let cool.
Heat sugar in a saucepan over medium heat, stirring constantly until melted into a deep amber. Whisk in butter until smooth, then slowly add heavy cream, whisking vigorously. Stir in sea salt if desired and let caramel cool slightly.
Remove chilled cheesecake from fridge. Spoon spiced apples evenly on top and drizzle with caramel sauce. Serve slices with extra caramel on the side.