Preheat oven to 350°.
Prepare crumb topping by mixing brown sugar, flour, oats, butter, cinnamon, nutmeg, and salt until mixture crumbles. Keep cold until ready to use.
Thinly slice four medium apples – I love Granny Smith.
In a medium pot, add apples, crushed pineapple, sugar, butter, cinnamon, nutmeg, lemon juice, and one cup water. Bring to a boil for 5 minutes.
In a small bowl, add cornstarch and remaining water. Mix and pour slowly into boiling filling. Stir until thickened.
Add vanilla and pour filling in pie crust. Add crumb topping on top of filling.
Bake for 30-45 minutes or until golden brown. Serve with vanilla ice cream on top.