Preheat oven to 325F. Press graham cracker crumbs, sugar, and melted unsalted butter firmly into a 9-inch springform pan to form an even layer, then bake 8 minutes until set and fragrant.

In a skillet, cook diced apples with 1 tablespoon butter, brown sugar, and cinnamon over heat 5 minutes until softened. Cool completely so the cheesecake filling stays smooth.

Beat softened cream cheese and granulated sugar until smooth, scraping the sides as needed. Add eggs one at a time, mixing just until combined after each addition for a silky batter.

Mix in sour cream, vanilla, and cinnamon until fully incorporated and glossy. Keep the batter uniform with no visible streaks.

Pour the cheesecake filling over the baked crust and smooth the top. Spoon the cooked apples over the filling in an even layer.

In a bowl, combine rolled oats, flour, brown sugar, and cinnamon. Cut in cold cubed butter until the mixture looks clumpy, then scatter the crisp topping over the apples.

Place the springform pan into a water bath setup on a sheet pan, with hot water coming about halfway up the sides. Bake 60-65 minutes at 325F until the center is just set and the edges look set while the middle still has a slight wobble.

Cool the cheesecake completely at room temperature until no longer warm to the touch. Refrigerate 6 hours before releasing and slicing for clean, creamy cuts.