01 - Preheat the oven to 350°F. Line a 9x9-inch baking pan with parchment paper, allowing overhang on sides for easy removal.
02 - In a large bowl, combine flour, sugar, and salt. Add cold cubed butter and cut in using a pastry cutter or fingers until mixture resembles coarse crumbs. Stir in vanilla extract.
03 - Reserve 1 1/2 cups of the crumb mixture for the topping. Press remaining dough firmly and evenly into the bottom of the prepared pan.
04 - Bake the crust for 12 minutes until slightly set. Remove from oven.
05 - While crust bakes, toss apple slices with lemon juice in a bowl. Add sugar, flour, and cinnamon, stirring until apples are evenly coated.
06 - Spread the apple mixture evenly over the hot crust. Drizzle caramel sauce over the apples.
07 - Sprinkle the reserved crumb mixture evenly over the apple and caramel layer.
08 - Bake for 28-32 minutes until the topping is light golden brown and apples are tender when pierced with a fork.
09 - Let cool completely in the pan, about 1 hour. Lift out using parchment overhang and cut into 16 bars.