Preheat your oven to 350 degrees F.
In a large bowl, combine the apples, sugar, water, cornstarch, cinnamon and nutmeg. Stir to combine. Spray the inside of a 9x13 baking dish with cooking spray. Add the apples to the dish.
In a small bowl, combine the oat flour, old-fashioned oats, brown sugar, cinnamon and softened butter. Stir with a fork until crumbly.
Add the topping to the apples. Bake for 30 minutes, until the apples are cooked through.
Serve with vanilla ice cream!