Preheat oven to 350℉. Line an 8" square light metal baking pan with parchment paper or foil, extending the sides of the parchment or foil over the edges of the pan. Spray the foil or paper lightly with cooking spray; set aside.
First, make your pastry crust. In a food processor, pulse together the flour and salt until mixed. Add in the egg yolk, cubed butter and milk and pulse until a soft dough comes together into a ball shape. Roll the dough ball in a piece of plastic wrap and briefly refrigerate while you prepare the filling.
Toss the diced, peeled apples together with the sugars, flour, spices and vanilla until fully coated. Set aside. For the Dutch crumble, mix together the melted butter, brown sugar, flour, cinnamon, and salt until crumbly. Set aside.
Unroll your pie dough in an 8" square shape. Place it evenly into the bottom of your prepared pan. Bake for 10-12 minutes or until slightly puffed. Remove from oven, but keep oven on. Top the crust with the apples in an even layer, as well as any juices from the apple bowl, followed by the Dutch crumble crumbled evenly over the top.
Return to the oven and bake for an additional 40-45 minutes or until light golden brown on the top and appears set. Cool completely in the pan before cutting into bars.