Butter a 9-inch deep dish pie plate (Pyrex is recommended).
Working on a well floured surface, roll out 1 piece of the dough to a thickness of about 1/8 inch; fit the dough into the buttered pie plate and trim the edges to ½ inch overhang.
Roll the other piece of dough into a 1/8 inch thick circle and slip it onto a baking sheet lined with parchment paper.
Cover both the circle and the crust in the pie plate with plastic wrap and refrigerate for 20 minutes, while you preheat the oven and prepare the filling.
Position oven rack in center of oven; preheat to 425°.
Peel, core, and slice the apples; put apples in a large bowl and add the sugar, lemon zest, tapioca, cinnamon, nutmeg, and salt.
Toss everything together well; if you have time, let the mix sit for about 5 minutes, until juice starts to accumulate in the bottom of the bowl.
Remove the pie plate and top crust from the refrigerator and put the pie plate on a baking sheet line with parchment paper.
Sprinkle the crumbs evenly over the bottom of the crust; turn the apples and their juices into the crust.
The apples will heap over the top of the crust, pat them down into an even mound.
Dot apples with the bits of cold butter.
Very lightly moisten the rim of the bottom crust with water; center the top crust over the apples.
Either fold the overhang from the top crust under the bottom crust and crimp the crust attractively, or press the top crust against the bottom crust and trim the overhang from both crusts even with the rim of the pie plate.
If you have pressed and trimmed the crust, use the tines of a fork to press the two crusts together securely.
Use a sharp paring knife to cut about 6 slits in the top crust.
Brush the top crust with a little milk or cream and sprinkle it with sugar.
Bake the pie for 15 minutes; decrease oven temperature to 375° and bake for another 50-60 minutes, or until the crust is gorgeously browned and the juices bubble up through the top crust.
After about 40 minutes in the oven, if the top crust looks as if it is browning too quickly, cover pie loosely with a foil tent.
Transfer pie to a rack and let it rest until it is only just warm or until it reaches room temperature.