Thaw frozen cherries in a colander over a medium bowl, reserving juice. Measure drained juice; add enough cherry juice or water to measure 3/4 cup.
Let piecrust stand at room temperature according to package directions. Unroll piecrusts. Ease 1 piecrust into a 9-inch pie plate, being careful not to stretch pastry. Do not prick pastry. Cut remaining piecrust in 1/2-inch wide strips; set aside.
In a medium saucepan, combine granulated sugar, cornstarch, cinnamon, salt, and allspice. Add the 3/4 cup reserved juice and butter. Cook and stir over medium heat until thickened and bubbly. Remove from heat. Stir in thawed cherries.
Pour filling into the pastry-lined pie plate. Weave strips over filling in a lattice pattern. Press strip ends into bottom pastry rim. Fold bottom pastry over strip ends; seal and crimp edge. To prevent overbrowning, cover edge of pie with foil.
Place pie on an oven rack positioned over a baking sheet on the rack below. Bake in a 375 degree F oven for 30 minutes. Remove foil. Bake for 30 to 35 minutes more or until filling is bubbly in the center and piecrust is golden. Cool on a wire rack for at least 2 hours before serving. To serve, sprinkle with some coarse sugar, if you like. Makes 8 servings.