Preheat the Oven: Preheat your oven to 325°F (163°C). Grease a 9-inch springform pan with butter or non-stick cooking spray to ensure easy removal after baking.
Prepare the Cheesecake Layer: In a large mixing bowl, beat 1½ cups of cream cheese and ¾ cup of sugar using a hand mixer or stand mixer on medium speed until creamy and smooth, about 2-3 minutes. Gradually mix in ½ cup of sour cream, 2 eggs, 1 teaspoon of vanilla extract, and 1 teaspoon of cinnamon until fully incorporated and smooth with no lumps.
Prepare the Apple Filling: In a separate bowl, combine 3 large diced apples with 1 tablespoon of lemon juice, ¼ cup of brown sugar, ½ teaspoon of cinnamon, ¼ teaspoon of nutmeg, and a pinch of salt. Toss the mixture until the apples are evenly coated.
Layer the Ingredients: Pour the cheesecake mixture into the prepared springform pan. Gently layer the spiced apple mixture over the cheesecake, pressing down gently to distribute the apples evenly without disturbing the cheesecake layer.
Prepare the Crisp Topping: In another bowl, combine 1 cup of oats, ½ cup of flour, ½ cup of brown sugar, ½ teaspoon of cinnamon, ½ cup of melted butter, and ¼ teaspoon of salt. Mix until the ingredients clump together into a crumbly mixture.
Bake the Cheesecake: Sprinkle the crisp topping evenly over the apple layer. Bake in the preheated oven for 60-70 minutes or until the edges are set and the center slightly jiggles. Turn off the oven and let the cheesecake cool inside for 1 hour with the door ajar.
Cool and Chill: Allow the cheesecake to cool to room temperature, then refrigerate for at least 4 hours or preferably overnight to firm up.
Serve: When ready to serve, carefully remove the sides of the springform pan. Cut the cheesecake into slices and serve chilled, optionally drizzling with caramel sauce or pairing with vanilla ice cream for added indulgence!