Preheat oven to 375°F (190°C). Line a rimmed baking sheet (9×13 or similar) with parchment paper.
Roll out one pie crust and press it gently into the prepared pan, covering the bottom and sides.
In a large bowl, toss apples with sugars, lemon juice, flour, cinnamon, nutmeg, and salt until evenly coated.
Spread the apple mixture evenly over the bottom crust.
Place the second crust over the apples or cut into strips for a lattice top. Trim and seal edges.
Cut small slits in the top crust if using a full crust.
Brush with egg wash and sprinkle with coarse sugar if desired.
Bake for 45–55 minutes, until the crust is golden and the filling is bubbling.
Let cool for at least 40 minutes before slicing.