Double the pie crust recipe and retain the egg whites (the dough recipe calls for egg yolks). Split the dough into two disks before refrigerating. Chill per the recipe.
For the Filling:
Preheat the oven to 425F.
Roll out the bottom crust into a pie plate. Return the rolled-out crust to the fridge while mixing the filling.
In a small bowl, using your fingers, massage together the sugar and lemon zest (about a minute). Whisk in the cinnamon. Set aside.
In a large bowl, grate the apple (do not peel). You should have about 3/4 cup grated apple (137g).
Add the berries to the grated apple. Add the flour and toss to coat evenly. Pour the sugar mixture over the berries, along with the lemon juice, and stir to coat.
Assemble the Pie:
Add the filling to the bottom crust. Return the pie to the fridge.
Roll out the top crust. A lattice topping (pictured) is recommended. A lattice top helps water evaporate from the filling to help it set. A full top crust may result in a looser filling. To make a lattice top, use a pizza cutter (or knife) to cut 6-8 strips of dough. Carefully lay each strip over the top of the filling, pressing the ends into the bottom crust.
Whisk the egg whites with a tiny bit of water. Brush the egg whites over the top of the crust. Optional: Sprinkle the crust with turbinado sugar.
Set the pie plate on a rimmed baking sheet.
Bake the pie in a 425F oven for 15 minutes. Baking your pie on the bottom/middle rack will help achieve a golden brown crust. Drop the oven temperature to 375F. Bake an additional 55-65 minutes, until the crust is golden and the filling is bubbling in the center of the pie.
Remove the pie from the oven and let it cool for at least 4 hours; 12 hours is best. Serve at room temperature with homemade whipped cream or vanilla ice cream. Store any leftover pie in the fridge.