In a bowl combine white sugar, flour, cornstarch, cinnamon, and nutmeg.
In a large bowl combine sliced apples and lemon juice, then add the mixed dried ingredients and using a spatula stir everything together until thoroughly combined. Set aside.
Preheat oven to 400°F (200°C).
Place pie crust in pie dish and tuck it in with your fingers. Trim excess dough if needed and flute the edges.
Spoon the apple filling into the crust but leave most of the liquid in the bowl.
To make the crumble topping, combine the flour, brown sugar, cinnamon, and butter cubes in a bowl and use a fork, pastry cutter, or your hands to combine until thick and crumbly. Sprinkle topping over apple filling.
Place pie dish on a large enough baking sheet covered with parchment paper and bake for 20 minutes. Then turn the temperature down to 375°F (190°C) and bake for 30 more minutes until the topping is golden brown and the filling is bubbling up. If the edges brown to quickly cover them with a pie shield after 20 minutes.
Let the pie cool completely before cutting into it to allow the filling to thicken up. Cover leftovers with plastic wrap and store in the fridge for up to 4 days.