Preheat your oven to 350°F (175°C) and prepare a 9x13 inch baking pan by lining it with parchment paper.

In a large mixing bowl, combine all-purpose flour, granulated sugar, and a pinch of salt. Cut in chilled butter until it resembles coarse crumbs.

Press about two-thirds of the crumb mixture into the bottom of the prepared pan and bake for 15 minutes until lightly golden.

Wash, peel, and slice the apples. Toss with brown sugar, cinnamon, nutmeg, cornstarch, lemon juice, and vanilla extract.

Layer the apple mixture evenly over the crust, then crumble the reserved mixture on top.

Bake for 35-40 minutes until the topping is golden brown and the filling is bubbling.

Let cool in the pan for easy slicing, then transfer to a cutting board and slice into bars.