Meanwhile, in 1-quart saucepan, mix sugar and cornstarch. Stir in reserved raspberry liquid. Cook over medium heat, stirring constantly, until mixture becomes clear and thickened. Stir in orange juice; cool at room temperature at least 10 minutes before serving. Serve individual servings of pie with sauce. If desired, garnish with fresh raspberries. Cover and store pie in freezer, sauce in refrigerator.