In a medium sized mixing bowl coat apples with ⅓ cup brown sugar and ½ tsp cinnamon. Thinly slice 3 tbsp of butter and layer in the bottom of a 12 inch cast iron skillet. Pour the apples over the butter.
In another mixing bowl combine remaining sugar, cinnamon, flour and melted butter until a fully incorporated. Using your fingers crumble over the top of the apples.
Bake on the center rack for 45 min or until bubbling. I think it goes without saying this should be served with vanilla ice cream.
