To make the crust:

1. Preheat the oven to 325 degrees, and line a 9 x 9 square pan with parchment paper. If the parchment paper doesn’t come up the insides of the pan, use butter or baking spray to grease the sides.
2. Pulse the cinnamon grahams and the brown sugar in a food processor until finely ground. Add the melted butter and pulse again until the crumbs are evenly and completely moistened.
3. Pour the moist crumbs into the prepared 9 x 9 pan. Using a spatula, your hands, or the bottom of a measuring cup, press the crumbs firmly over the bottom of the pan. Make sure to get it evenly packed, especially into the corners.
4. Bake the crust for 8-9 minutes and remove from the oven. Leave the oven set to 325 degrees. Allow the crust to cool completely before adding the filling.

To make the apple and oat streusel toppings:

1. For the apple topping, toss the sliced apples with the cinnamon and cardamom until evenly coated.
2. Melt the butter in a skillet over medium heat until it begins to sizzle. Add the spiced apples and cook for 2 minutes until tender crisp and hot.
3. Transfer the apples to a large paper towel lined plate or platter and allow to cool while you make the oat topping and cheesecake filling.
4. For the oat streusel topping, pulse the flour, brown sugar, cinnamon, nutmeg, salt and butter in the bowl of a food processor until the butter has been incorporated and the mixture looks like coarse crumbs. Add the mixture to a small bowl and stir in the oats. Set aside while you prepare the cheesecake filling.

To make the cheesecake filling:

1. Pulse the cream cheese, sour cream, sugar and flour in the bowl of a food processor until smooth. This should only take a few seconds. Add the first egg and pulse for a few seconds to combine, and scrape down the bowl. Add the remaining egg, vanilla extract and lemon juice all at once, and pulse for another couple seconds to combine.
2. Scrape down the processor bowl well, making sure to mix in any lumps or unmixed ingredients, and pour the filling into the cooled graham crust. Spread the filling into an even layer.

To add the toppings and bake:

1. Spread the softened, spiced apples into even layers over the cheesecake filling. This will take some time, and you will end up with 2-3 layers of apples. Be sure to evenly distribute them over the surface, patching up any open spots. Use all of the apple slices.
2. Sprinkle the oat streusel topping over the apples, creating an even layer.
3. Bake the cheesecake bars in the preheated oven for 43-45 minutes. The oat topping should be lightly golden.
4. Cool to room temperature and refrigerate for at least 4 hours. Ideally, chill overnight to set the cheesecake filling.
5. Before serving, drizzle the cheesecake bars with salted caramel sauce and slice into 16 squares.