1. Preheat oven to 375°. On a lightly floured surface, unfold dough, and roll to 10 by 15 inches. Cut into two 10-by-7 1/2-inch rectangles. Refrigerate until cold.
2. Stir pears, cherries, sugar, cornstarch, lemon juice, salt, pepper, and spice powder in a bowl.
3. Transfer 1 rectangle of dough to a baking sheet lined with parchment. Spoon fruit mixture onto dough, leaving a 1-inch border all around. Brush border with beaten egg. Lay remaining dough over filling; press gently to seal. Refrigerate 20 minutes. Transfer to a room-temperature rimmed baking sheet lined with parchment.
4. Trim edges, and brush top with beaten egg. Cut five 5-inch vents in top. Sprinkle with sugar. Bake, rotating once, until crust is golden and juices are bubbling, about 35 minutes. Transfer pie to a wire rack; let cool 20 minutes before serving.