Preheat the oven to 450 degrees (F) and place a rimmed baking sheet on the center rack while the oven is preheating. Reserve a piece of parchment paper or foil to fit the baking sheet to be used at the time of baking.
Make the gluten free pie crust as directed and chill for 1 hour.
To make the filling, place the thinly sliced apples in a large bowl and toss with the lemon juice.
In a separate medium/small bowl, whisk together the granulated sugar, light brown sugar, cornstarch, cinnamon, nutmeg, cloves, and salt. Break down any lumps.
Pour the sugar/spice mixture over the apples and gently mix well to coat all the apples, then set aside.
In a small bowl, make the egg wash by beating the egg and whisking in the cream. Set aside until ready to use.
Roll out the 1/2 of the chilled crust and place it in a deep-dish pie plate, leaving enough crust as an overhang. Brush the bottom crust with egg wash if desired (see the tips section in the post).
Layer the apples evenly in the crust instead of just pouring the apples in. Having flat layers of apples will help the pie keep it's shape better and it will help prevent air pockets in the pie. Taking the time to layer the apples is a bit more tedious and time-consuming but worth the effort.
Once the apples are layered, pour any excess liquid from the apple bowl over the apples and scatter the cubed butter on top of the apples. Roll out the top crust and carefully place the crust on top of the pie. Gently press the crust down on top of the apples so that it's resting directly on top of them.
Press the crusts together and crimp the edges to seal the crust. Trim the excess crust before crimping, if needed (I usually don't need to).
Place the pie in the refrigerator and chill for 30-45 minutes before baking. This will help the butter in the crust get cold to make a flaky crust once baked.
Once the pie has chilled, remove it from the fridge and brush the top of the pie and the crust with the egg wash. Use a sharp paring knife to cut several slits in the top of the pie for venting. Be sure to make the cuts deep enough to go through the crust and wide enough that they don't close. Sprinkle the pie with coarse sugar, if desired.
Carefully place the parchment paper (or foil) on the preheated sheet pan and place the cold pie on top. Bake on the center rack at 450 degrees for 10 minutes.
After 10 minutes, lower the temperature to 350 degrees and bake the pie for 45-80 minutes. Tent the pie with aluminum foil to prevent the crust from getting too brown, if needed.
When the pie is done, the filling will be bubbling along the edges and in the vents, the apples will be soft when tested with a knife, and the internal temperature is at least 175 degrees F. For best results, the pie should be bubbling for at least 5-10 minutes before removing from the oven.
Cool the pie on a wire rack for at least 4 hours before serving so the filling can set. Serve at room temperature or chill before serving. (See the tips section of the post for cutting clean slices.)