Preheat the oven to 375F.
In a large mixing bowl, combine the apples, lemon juice, sugars, flour, cinnamon, and vanilla and mix to combine. Set aside.
6 cups granny smith apples, 1 tbsp lemon juice, ⅓ cup light brown sugar, ⅓ cup granulated sugar, ¼ cup all-purpose flour, 1 tsp ground cinnamon, ½ tsp vanilla extract
For the topping, combine all the ingredients in a mixing bowl and, using a pastry cutter or fork, blend the mixture until coarse crumbs form. Using your hands, squeeze the mixture together until all the butter is absorbed and your crumb topping comes together.
1 cup all-purpose flour, ⅓ cup granulated sugar, ⅓ cup light brown sugar, ½ cup chilled unsalted butter
Spread the apples evenly into the pie crust, discarding any liquid from the apples. Sprinkle the topping over the apples.
1 9-inch store bought pie crust
Bake the pie on the lowest rack for 50-60 minutes or until the apples and topping are bubbly and golden brown.
Let rest to room temperature before slicing and serving.