Start by making a flaky pie crust recipe to get two 9-inch pie crusts, one for the bottom and one for the top, chilling the dough for at least an hour before rolling it out, or use store-bought crusts following the package instructions.
Position a rack in the middle of your oven and heat it to 400°F (204°C).
In a large bowl, toss the apple slices with granulated sugar, light brown sugar, flour, cinnamon, nutmeg, lemon juice, and lemon zest until coated well.
Take out your pie dough from the fridge, let it sit for 5 to 10 minutes at room temperature, then roll one disc on a floured surface into a 12-inch circle about ⅛ inch thick, and place it gently into a deep pie plate.
Fill the crust with the apple mixture, discarding any excess juice, then roll out the second dough disc similarly and cover the apples with it.
Trim the edges of the dough to the pie plate’s edge, pinch and fold the edges together neatly all around, then cut four slits in the top crust to allow steam to escape before setting the pie on a baking sheet.
Brush the top crust lightly with the beaten egg and sprinkle with sanding sugar if using. Protect the edges with a pie shield or foil to prevent excessive browning for the first 25 minutes.
Bake the pie at 400°F (204°C) for 25 minutes, then carefully remove the edges’ cover, reduce the oven temperature to 375°F, and bake for an additional 30 to 35 minutes until the crust is golden and the filling bubbles.
Let the pie cool on the counter for a minimum of three hours to set before serving.
