For crust: In the work bowl of a food processor, place flour, cornmeal, and salt; pulse until combined. Add butter and pulse until mixture is crumbly. Add water, 1 tablespoon at a time, pulsing until a dough forms. Turn out dough, and shape into a disk. Wrap in plastic wrap, and refrigerate for 1 hour.
For filling: In a small bowl, combine cranberries and 1 cup boiling water. Let stand until softened, about 20 minutes. Drain.
Preheat oven to 375°.
In a large bowl, toss together cranberries and apples. Sprinkle with granulated sugar, flour, lemon juice, apple pie spice, and salt; toss well.
Spoon into a shallow 11x7-inch baking dish. Sprinkle with butter.
Let dough stand at room temperature until slightly softened, about 10 minutes. On a lightly floured surface, roll dough into a 12½x8½-inch rectangle. Trim to straighten edges. Cut dough lengthwise into 7 equal strips. Place 3 strips of dough lengthwise over filling. Place remaining 4 strips of dough crosswise over filling. Trim excess dough.
In a small bowl, whisk together egg and 2 teaspoons water; brush over dough. Sprinkle with sparkling sugar.
Bake until crust is golden brown and filling is bubbly, about 40 minutes. Let cool on a wire rack.
Recipe by Southern Lady Magazine at https://southernladymagazine.com/apple-cranberry-cobbler-recipe/