Preheat the oven to 400 degrees F. Move the oven rack to the bottom third of the oven.
Divide the dough in half and set one half aside; cover it with a towel or plastic wrap to keep it from drying out. On a lightly floured work surface, roll out the dough to a 10-inch round. Loosely drape the dough round over the rolling pin and transfer to a 9-inch pie pan. Press the dough over the bottom and sides of the pan. Trim the edges to about 1/2-inch.
Toss the fruit with the sugar, lemon, and cornstarch. Pile the fruit into the pie shell and dot with the butter. Roll out the reserved dough to a 9 to 10-inch round and lay it over the fruit. Trim, and crimp the edges. Cut 2 or 3 (2-inch) vents in the top of the pie and brush with the egg glaze. Put the pie on a baking sheet and bake until the crust is golden brown and the juices are bubbling up through the vents, 50 to 60 minutes. Cover the edges with aluminum foil if they brown too fast. Cool on a rack before serving. Serve with vanilla ice cream.
Combine the flour, sugar, salt, and lemon zest in a large mixing bowl. Add the butter and mix with a pastry blender or your fingers until the mixture resembles coarse crumbs. Add the egg yolk and ice water and work that in with your hands. (Or do the whole thing in a food processor, pulsing a couple of times to combine the dry ingredients, then pulsing in the butter, and then the egg.) Check the consistency of the dough by squeezing a small amount together between thumb and forefingers: You want there to be just enough moisture to bind the dough so that it holds together without being too wet or sticky. If it's still crumbly, add a little more ice water, 1 teaspoon at a time. When you get it to the right consistency, shape the dough into a disk and wrap it in plastic. Put it in the refrigerator and chill for at least 30 minutes.