Combine the flour, sugar, and salt in a large bowl. Add the butter and, using a pastry blender, cut the butter into the flour mixture until the butter pieces are the size of small peas. I tend to shake the bowl every so often, so that the larger butter pieces accumulate at the top and I can target them with the pastry blender.

Drizzle the water over the butter and flour mixture. As you drizzle the water, "fluff" the flour mixture with a fork - this really helps distribute the water evenly. You can stop adding the water for a bit, fluff the dough mixture with the fork, then target dry patches with additional water. After you've added all the water, knead until the dough comes together in a ball. When you pick up the dough in your hand and squeeze, the dough should stay together and should not crumble.

Transfer to a generously floured work surface, and roll into approximately a 10-by-15 inch sheet. Fold each 10-inch side toward the middle so that the edges meet, then close the packet like a book. Fold again top to bottom, and divide the block of dough in half. Wrap each half in plastic wrap, and refrigerate for at least 1 hour (preferably 2), or overnight. 

Remove one piece of dough from the refrigerator - if necessary, let stand at room temperature until malleable. Roll dough on lightly floured work surface or between two large sheets of plastic wrap to about a 13-inch round. Transfer dough to a 9-inch pie plate by rolling dough around rolling pin and unrolling over the plate or by folding dough in quarters, then placing dough in pie plate and unfolding. Ease dough into plate by gently lifting dough edges with one hand and pressing down into the plate bottom and sides with your other hand. Leave dough that overhangs lip of plate in place, and refrigerate.

Wash and pit fresh cherries; see note above if you do not have a cherry pitter. Combine the pitted cherries with the lemon juice, sugar, salt, and tapioca flour or instant tapioca. Toss gently with a flexible spatula to combine. Pour into the prepared pie shell and refrigerate while you roll out the top crust.

Roll out second piece of dough to about an 11-inch round and place over filling. Gently press the top and bottom pieces of pie dough together, and fold and tuck the dough underneath itself so that the outer edge of crust is flush with the outer edge of pie plate. Flute the crust by pinching with your fingers or press with fork tines if desired, but I found that with such a buttery crust, the decorative crimping tended to melt away when baked. Cut several slits on dough top. Refrigerate the entire pie until firm and cold, about 30 minutes. Meanwhile, preheat oven to 425°F.

Take pie out of refrigerator and brush egg white onto top of crust. Sprinkle evenly with sanding sugar, if desired. Place pie on baking sheet and bake until top crust is golden, about 25 minutes. Rotate pie and reduce oven temperature to 375°F; continue baking until juices bubble and crust is deep golden brown, 30-35 minutes longer. If the crust is browning too quickly, loosely cover the pie with aluminum foil.