Preheat oven to 350°F. Line a 9×13-inch pan with parchment paper and spray with non-stick baking spray.

In a stand mixer or large bowl, beat butter and both sugars until light and fluffy, about 2-3 minutes. On low speed, add flour and mix until combined; the dough will be crumbly.

Press the dough evenly into the bottom of the prepared pan. Bake for 16 minutes. Remove from oven and set aside to cool, keeping oven temperature at 350°F.

In a large bowl, combine apples and lemon juice, tossing to coat. Add cinnamon, flour, sugar, and salt. Toss until apples are evenly coated and arrange evenly on top of the crust.

In a large bowl, combine oats, both sugars, cinnamon, and flour. Add cubed butter and cut into the dry ingredients until the mixture resembles a coarse meal.

Sprinkle the topping evenly over the apples.

Bake for 45 to 50 minutes, or until the top is golden brown and apples are bubbling.

Remove from oven and place the pan on a cooling rack. Cool for at least 1 hour before serving.