In a large bowl, mix together 2 1/2 cups flour and the salt. Add the butter and, using your fingers, blend until the mixture resembles coarse crumbs. Sprinkle in the ice water and mix until the dough just holds together (if necessary, mix in 1 tablespoon more ice water at a time).
Turn out the dough, gather into a ball, then halve the dough ball. Pat each half into a disk, wrap with wax paper and refrigerate for 15 minutes.
Position a rack in the lower third of the oven and preheat to 400. On a lightly floured work surface, using a rolling pin, roll out 1 disk into a 13-inch round. Roll the dough onto the rolling pin, then unroll it over a 9 1/2-inch pie pan. Press the dough into the bottom of the pan, letting the excess hang over the edges. Refrigerate.
Peel and coarsely chop the apples and pears; place in a large bowl. Add the cranberries, 3/4 cup sugar and the lemon juice and toss. Sprinkle with the remaining 1/3 cup flour and toss. Pour into the chilled pie shell and set aside.
On a lightly floured work surface, roll out the remaining dough into a 13-inch round. Roll the round onto the rolling pin and unroll over the filling. Trim the excess dough, leaving a 1-inch overhang. Roll up the edges of the crusts and crimp. Cut three vents into the center of the pie. Brush the crust with water and sprinkle with sugar.
Bake the pie until golden, about 1 hour and 10 minutes. Transfer to a wire rack and let cool completely.