Rustic Grape Tart

Preheat oven to 400u0b0.
To prepare crust, lightly spoon 1 cup flour into a dry measuring cup; level with a knife. Combine 1 cup flour, cornmeal, 3 tablespoons granulated sugar, baking powder, and salt in a food processor; pulse 4 times or until blended. Add chilled butter; pulse 6 times or until mixture resembles coarse meal. With processor on, slowly pour orange juice through food chute, processing just until blended (do not allow dough to form a ball).
Press mixture gently into a 4-inch circle on plastic wrap; cover. Chill for 15 minutes. Slightly overlap 2 sheets of plastic wrap on a slightly damp surface. Unwrap and place chilled dough on plastic wrap. Cover dough with 2 additional sheets of overlapping plastic wrap. Roll dough, still covered, into an 11-inch circle. Remove top sheets of plastic wrap; place dough, plastic wrap side up, on a baking sheet lined with parchment paper. Remove plastic wrap. Sprinkle dough with 1 teaspoon flour.
To prepare filling, combine grapes, 2 tablespoons granulated sugar, cornstarch, vanilla, and cinnamon. Spoon into center of dough, leaving a 2-inch border. Fold edges of dough toward center, pressing gently to seal (dough will only partially cover grape mixture). Combine water and egg yolk; brush over edges of dough. Sprinkle turbinado sugar over grape mixture and dough, if desired. Bake at 400u0b0 for 25 minutes or until crust is brown. Serve warm or at room temperature.