Preheat oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper.
Mix 1 1/2 cups flour, 1/2 cup brown sugar, 1/4 teaspoon salt, and 1/2 teaspoon cinnamon in a bowl. Add cold butter and use a pastry blender or fork to combine until the mixture resembles coarse crumbs.
Mix the crushed graham crackers or ground shortbread into the butter-sugar mixture until evenly blended. Press into the bottom of the prepared pan and bake for 15 minutes. Set aside to cool.
While the crust bakes, prepare the cheesecake layer. In a bowl with an electric mixer, beat cream cheese until smooth. Add sugar, vanilla, and lemon zest. Mix until fluffy. Spread evenly over the cooled crust. Return to the oven and bake for another 15–20 minutes. Let cool completely.
Prepare the apple filling by mixing chopped apples, apple butter, maple syrup, cinnamon, and nutmeg until well combined. Spread in an even layer over the cooled cheesecake layer.
For the streusel, combine flour, brown sugar, 1/2 teaspoon cinnamon, and 1/4 teaspoon salt in a bowl. Add cold butter and mix with a fork until crumbly. Sprinkle over the apple layer.
Bake for 20–25 minutes, or until the streusel is golden. Remove and let cool completely.
For the caramel drizzle, heat sugar in a small saucepan over medium-high heat until golden amber. Remove from heat and slowly pour in cream (carefully, as it will bubble up). Add butter and sea salt, stirring until blended. Drizzle the caramel over the cooled cheesecake bars.
Chill for at least 2 hours before cutting into bars.
Serve and enjoy!