Peel, core, and slice 8 Granny Smith apples into thin, uniform ⅛-inch slices. Toss them with granulated sugar, flour, lemon juice, lemon zest, cinnamon, nutmeg, and salt. Let the mixture sit for 20–30 minutes to release excess moisture.
Preheat your oven to 400°F (205°C). Place the prepared pie crust into a 9-inch glass pie dish and crimp the edges. For extra protection against a soggy crust, brush the bottom lightly with beaten egg white.
Make the crumble topping by combining flour, brown sugar, granulated sugar, and cinnamon. Add the chilled cubed butter and cut it into the dry ingredients with a fork until crumbly.
Layer the prepared apples into the pie crust, filling it to the top. Pour any leftover apple juices over the apples.
Spread the crumble topping evenly over the apples, pressing it down lightly. Place the pie dish on a cookie sheet to catch any drips.
Bake at 400°F for 20 minutes, then reduce the oven temperature to 375°F (190°C) and continue baking for 35–45 minutes. If the crust edges brown too quickly, cover them with aluminum foil. The pie is done when the apples are soft when pierced with a fork or knife.
Let the pie cool slightly before serving. Serve warm or at room temperature, preferably with a scoop of vanilla ice cream.