Preheat oven to 350 degrees.
Peel and core apples, then slice thinly.
Put the apples in a large zip top bag and add ½ cup white sugar, ½ teaspoon of cinnamon and 1 ½ teaspoons of flour. Zip bag and shake to coat all the apples evenly.
Pour the coated apples into a pie pan.
To make the topping, combine brown sugar, flour, oats, baking soda, baking powder, and nutmeg in a bowl. Add the melted butter and mix until crumbs are formed.
Generously sprinkle the crumbs over the apples.
Bake at 350 degrees for 50 minutes.
Serve with vanilla ice cream if desired.