In a large mixing bowl, whisk together flour, granulated sugar, and salt. Cut in the cold cubed butter until the mixture resembles coarse crumbs with pea-sized pieces of butter.
Drizzle in ice water one tablespoon at a time, mixing gently until the dough just comes together. Divide into two discs (one slightly larger), wrap in plastic, and refrigerate for at least 1 hour.
Peel, core, and slice apples into ¼-inch thick slices. Toss with lemon juice and zest. Mix sugars, flour, cinnamon, and nutmeg, then coat the apples evenly. Set aside.
Roll out the larger dough disc on a lightly floured surface to a 12-inch circle. Transfer to the 9-inch pie dish, trim overhang, and chill while preparing the top crust.
Roll out the second dough disc to a 12-inch circle for the top crust (or cut into strips for lattice). Chill until ready to assemble.
Preheat oven to 400°F with a baking sheet on the lower rack. Pour apple filling into the bottom crust, dot with butter pieces, and mound slightly in the center.
Place top crust over filling, trim and crimp edges. Cut vents if using a solid crust. Brush with egg wash and sprinkle with coarse sugar.
Bake at 400°F for 20 minutes, then reduce to 375°F and bake 35-45 minutes until crust is deep golden and filling bubbles. Tent edges with foil if needed.
Cool pie on a wire rack for at least 3-4 hours before slicing to allow filling to set.