Preheat your oven to 350 degrees F.
For the apple portion:
Slice apples thinly and put them in a medium sized bowl.
Sprinkle the sugar, corn starch, cinnamon and nutmeg over apples in the bowl. Mix until well combined.
Transfer to a 9 x 13 pan that you've sprayed with non stick spray.
For the topping:
Mix the flour, sugars, and butter in a bowl. Cut the butter into it with a pastry cutter or fork. It should look sort of like wet sand.
Add the cinnamon and nutmeg. Mix again.
Toss the topping over the apple mixture.
Pop the dish in the oven and bake for about 35 to 45 minutes depending on your apple type and oven. I start checking at 35 but most times it's done in about 40.