For crust:
Mix all crust ingredients in pie pan and shape.
For filling:
In a large bowl, combine sliced apples with sugars, lemon juice, cinnamon, nutmeg and salt.
Let sit at room temperature for 30 minutes or up to 3 hours. Place apples in strainer over large bowl and let sit until you collect 1/2 c of liquid.
Preheat oven to 425.
Take collected juices and add 2 Tb butter in small saucepan and heat until liquid becomes syrup and caramelized.
Transfer apples to large bowl and mix in cornstarch. Pour syrup over apples and transfer to crust.
Cover loosely with foil and put in preheated oven . Bake 10 minutes.
For topping:
Mix first 4 topping ingredients together until crumbly. Cut in butter until entire mixture is moist.
Reduce heat to 375. Sprinkle topping over apples. Return to oven uncovered.
Bake 45 minutes.
Let cool 15 minutes before cutting.