Preheat oven to 425.
Place apple slices in a large deep bowl. Slice the lemon in half and sprinkle a good squeeze of lemon juice over the apples and toss to coat.
In a separate bowl, mix the cornstarch, sugars cinnamon, nutmeg, and salt. Set aside.
Pour the apple cider over the apples adding 1 tsp or liberal pinch of the lemon zest. Toss with your hands and allow to stand 10 minutes or so. Then add sugar mixture and butter to apples and gently toss.
Using your hands, scoop the apple mixture into the prepared crust, leaving the liquid in the bow. The crust will be full. Add the top crust, pinch down the sides in your favorite fashion.
Brush with egg wash. Cut 6 small slits in the top to allow the steam to escape.
Turn down oven to 350 and place pie on middle rack. Bake for 1 hour, observing closely the last 15 minutes as all ovens are not created equally! Top crust should be nicely browned. Let cool slightly before serving.