Prepare the Pie Crust: In a large bowl, whisk together flour and salt. Cut in cold butter using a pastry blender or your fingertips until crumbly. Gradually add ice water, 1 tablespoon at a time, mixing until dough just comes together. Divide dough in half, flatten into discs, wrap in plastic, and chill for at least 30 minutes.

Prepare the Filling: In a large bowl, combine sliced apples, granulated sugar, flour, cinnamon, nutmeg, and lemon juice. Toss gently to coat.

Assemble the Pie: Preheat oven to 425°F (220°C). On a lightly floured surface, roll out one dough disc into a 12-inch circle. Carefully transfer to a 9-inch pie plate. Trim edges, leaving a 1/2-inch overhang.

Add Filling: Pour the apple mixture into the pie crust. Dot the top of the apples with small pieces of butter.

Top Crust: Roll out the second dough disc. Place it over the apple filling. Trim and crimp the edges to seal, or create a lattice top. Cut several slits in the top crust (if not making lattice) for steam to escape.

Bake: Brush the top crust with an egg wash (if using) for a golden sheen. Bake for 15 minutes at 425°F (220°C). Reduce oven temperature to 375°F (190°C) and continue baking for 35-45 minutes, or until the crust is golden brown and the filling is bubbling. If crust browns too quickly, cover edges with foil.

Cool and Serve: Let the pie cool on a wire rack for at least 30 minutes before slicing and serving. This allows the filling to set. Serve warm.