Begin by making the filling. Melt 2 tablespoons of butter in a large pan on medium-high heat. Add the apples and allow them to cook for about five minutes. Then stir in the brown sugar and cinnamon. Adjust the heat to medium and allow the apples to cook for about 10 more minutes until they are tender and the sauce is thick. Remove from heat. Set aside and allow to cool completely.
Preheat your oven to 425 degrees F. Spray a 10-inch cast iron skillet (or pie dish) with baking spray. Place the pizza dough inside the pan, shaping it to cover the bottom of the pan and the sides. If the dough is hanging over the sides, tear it off and pinch it back to another area where the dough is not covering the pan.
In a small dish, combine 2 tablespoons sugar and 1/2 teaspoon of cinnamon. Brush the dough with butter, then sprinkle with cinnamon-sugar mixture. (You might not use all of the butter or cinnamon sugar.)
In a large bowl, make the crumb topping by combining the butter, sugar, brown sugar, cinnamon and salt until crumbly. Squeeze the mixture in your hands to create larger crumbles.
Then, add the cooled apples to the top of the dough. Sprinkle the crumb topping evenly on the apples. Use as much or little of the crumb topping as you like.
Bake for 10 - 12 minutes or until the crust is golden.
In the meantime, in a small bowl, whisk together the powdered sugar, vanilla, and milk. Add one tablespoon of milk at a time until the desired consistency is reached.
Once the pie is removed from the oven, allow it to cool. Drizzle with the glaze and serve with ice cream, if desired.