Preheat oven to 450.
Prepare the bottom crust by rolling out one of the pastry disks to an 11 inch circle.
Nestle the crust inside the pan so about an inch hangs over the sides. Press the pastry down. Cover loosely with plastic wrap and place in the freezer for about 10 minutes.
Mix the fruit with sugar, flour or cornstarch, and lemon zest. Using the times of a fork, poke the bottom of the pie crust evenly about 5 minutes. Pour the fruti mixture into the chilled pastry. Dot with the butter pieces.
Moisten the edge of the bottom crust with a finger dipped in water. Put on the top pastry in one piece and slice in a few air vents, or in a lattice pattern, trim, and crimp the edges.
Brush the egg glaze over the crust. Transfer the pie to a baking sheet.
Bake in the oven for 15 minutes, then reduce the heat to 350 and bake another 30 minutes longer, or until crust is golden brown and the filling is bubbly.
Remove from the oven and cool on a rack before serving.