Preheat the oven to 350F (after you've cored and peeled the apples) and grease a 9 x 13 casserole dish with butter or ghee.
Using a mandolin on the thickest setting, slice apples into thin slices. Immediately toss them with two teaspoons lemon juice.
Add the apples to your casserole dish.
Mix the remaining of the filling ingredients in a separate bowl then pour the mixture over the apples and mix until they are coated well.
Mix all of the topping ingredients in the same bowl you used to mix the filling ingredients before you poured them over the apples. Once the topping ingredients are well combined. Spread the topping over the top of the apples.
Bake at 350F for 20-25 minutes then broil for 1-2 minutes or until the topping is golden brown. DO NOT OVERBOIL OR IT WILL BURN! Watch it like a hawk when it's under the broiler!