Preheat oven to 425°F (220°C) before starting to make the filling
Peel, core, and slice the apples into ¼-inch slices.
In a large bowl, combine the sugar, cornstarch, cinnamon, nutmeg, and salt.
Add the apples and lemon juice, tossing until the apples are evenly coated.
Spoon the filling into an unbaked 9-inch pie crust, mounding slightly in the center.
Dot with 1–2 tablespoons of butter (optional, but recommended for a richer filling).
Cover with the top crust or lattice crust. Trim, seal, and crimp the edges. Cut slits in a solid top crust to vent steam.
Bake at 425°F for 10 minutes, then reduce the oven temperature to 350°F (190°C) and bake for an additional 35–45 minutes, or until the crust is golden brown and the filling is bubbling.Cool for at least 2–3 hours before slicing to allow the filling to set.