Preheat the oven to 350 degrees F. Line a 13x9-inch baking pan with parchment paper, leaving a little overhang on the sides for easy removal.

In a medium bowl, combine the graham cracker crumbs, brown sugar, cinnamon, and melted butter. Stir until the crumbs are evenly moistened. Press the crust mixture firmly and evenly into the bottom of the prepared pan.

Bake for 8 to 10 minutes. Remove from the oven and let cool slightly while you prepare the filling.

In a large bowl, beat the softened cream cheese and granulated sugar until smooth and creamy. Add the eggs one at a time, mixing just until combined after each addition. Add the sour cream, vanilla, and salt. Mix just until smooth and combined. Pour the cheesecake filling over the crust and spread it into an even layer.

Spoon the apple butter in small dollops over the cheesecake filling. Use the tip of a knife or a skewer to gently swirl it through the cheesecake. Avoid overmixing so you still have visible ribbons of apple butter.

To make the crumble, combine the flour, oats, brown sugar, cinnamon, salt, and pecans (if using). Add the melted butter and stir until the mixture is crumbly. Sprinkle the crumble evenly over the cheesecake.

Bake for 35 to 42 minutes, or until the edges are set and the center still has a slight jiggle.

Let the bars cool completely at room temperature, then refrigerate for at least 3 hours or overnight.

Lift the cheesecake from the pan using the parchment paper. Slice into bars and serve chilled.