Preheat the oven to 350 degrees F. Take out a 9 x 13 baking pan.
Peel (if desired), core, and dice your apples.
Toss the apples with the orange and lemon zest and juice, sugar, flour, cinnamon, and nutmeg. Set aside.
Mix together the flour, sugars, salt, and cinnamon for the crumble in a bowl.
Add in the butter and use a pastry cutter or your hands to squeeze or cut in the butter into the flour mixture until it resembles large crumbs.
Pour the apples into the baking pan. Sprinkle the crumbles over the apples.
Bake for 30 - 45 minutes, or until the filling is bubbling and the top is golden brown. If your crumble is browning too fast, place aluminum foil over the crumble and continue baking until the filling is bubbly.
Allow the apple crumble to rest and cool so the filling can thicken.
Serve warm or room temperature, preferably with a scoop of ice cream.