Preheat the oven to 350?F (175?C).

In a mixing bowl, toss the sliced apples with lemon juice, granulated sugar, and cinnamon.

Spread the apple mixture evenly in a baking dish.

In another bowl, combine flour, brown sugar, rolled oats, and salt.

Add the cold, cubed butter and mix until the mixture resembles coarse crumbs.

Sprinkle the crumble topping evenly over the apple filling.

Bake in the preheated oven for 30 minutes or until the topping is golden brown and the apples are tender.

Let cool for a few minutes before serving.