Preheat oven to 350°F. Line on bottom and sides an 8 x 8 or similar size pan with parchment paper.
To a large bowl or food processor add the flour, brown sugar, salt and butter. Mix or pulse until combined and begins to stick together. Transfer 1/2 of the dough to the baking pan and press down into the pan with the bottom of a measuring cup. Bake in preheated oven for 15 minutes. Allow to cool.
To the remaining dough add 1/2 of the pie spice and toss to combine. Set aside.
In a mixing bowl, place the apples, sugar, vanilla, remaining pie spice, cornstarch and lemon juice. Stir until well combined. Scrape into baking pan, spreading the apples out to cover the baked dough completely. Sprinkle over the reserved dough, to completely cover the the apple mixture.
Bake in oven for 45 - 55 minutes until browned and bubbling on the sides. Remove from oven and let cool in pan. Remove using the sides of the parchment paper, cut and serve.