Preheat your oven to 350°F (175°C) and lightly grease a baking dish with butter or non-stick spray.
Peel, core, and thinly slice the apples, then toss them with half of the sugar and ground cinnamon in a mixing bowl until well coated. Spread the apple slices evenly in the baking dish.
In a separate bowl, combine the flour, brown sugar, and remaining sugar. Add the cold, cubed butter and use a pastry cutter or your fingers to work the butter into the dry ingredients until the mixture resembles coarse crumbs.
Sprinkle the crumb mixture evenly over the apples, covering them completely for a thick topping layer.
Place the baking dish in the oven and bake for about 40 minutes, or until the filling is bubbling and the topping is golden brown and crispy.
Remove the dessert from the oven and allow it to cool slightly. Serve it warm, with a scoop of vanilla ice cream or a dollop of whipped cream if desired.