Prepare the filling by placing the sliced apples in a large mixing bowl. Add granulated sugar, ground cinnamon, ground nutmeg, and all-purpose flour. Toss until the apples are evenly coated and set aside to marinate for 10 minutes.
6 cups peeled and sliced apples, 1/2 cup granulated sugar, 2 tsp ground cinnamon, 1/4 tsp ground nutmeg, 2 tbsp all-purpose flour
Preheat the oven to 425°F (220°C). Roll out one pie crust on a floured surface into a circle that fits your pie dish. Carefully transfer the crust into the dish, pressing gently to fit the bottom and sides, and trim excess crust near the edges.
1 package store-bought pie crusts
Pour the prepared apple filling into the crust, spreading it out evenly. Roll out the second pie crust and place it over the filling. Trim excess edges, then crimp the crust edges together to seal the pie.
Mix the beaten egg with water to create an egg wash. Brush the top crust with the egg wash using a pastry brush to ensure a glossy, golden finish. Cut a few small slits in the top crust to allow steam to escape during baking.
1 egg beaten, 1 tbsp water
Bake the pie in the preheated oven for 45 minutes or until the crust is golden brown and the filling is bubbling through the slits. During baking, you'll notice the crust turning a rich golden hue and a fragrant aroma filling the kitchen.
Allow the pie to cool for at least 30 minutes before serving to let the filling set. Serve warm or at room temperature, optionally with ice cream or whipped cream.