01 - Preheat oven to 350°F. Line a 9x9-inch baking pan with parchment paper, allowing overhang for easy removal.
02 - In a large bowl, combine flour, sugar, and salt. Add cold 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 topping. Press remaining dough evenly into the bottom of the prepared pan to form the crust.
04 - Bake the crust for 12 minutes until lightly set. Remove from oven.
05 - While crust bakes, combine apple slices with lemon juice in a bowl. Add sugar, flour, and cinnamon, tossing until apples are evenly coated.
06 - Spread apple mixture evenly over the hot crust. Drizzle caramel sauce over the apples.
07 - Sprinkle reserved crumb mixture evenly over the apples and caramel.
08 - Bake for 28 to 32 minutes until topping is light golden brown and apples are tender when pierced with a fork.
09 - Let bars cool completely in the pan. Lift out using parchment paper overhang and cut into 16 equal bars.