In a large saucepan, combine sugar, cornstarch, salt and if desired, cinnamon. And water and stir until smooth; add blueberries. Bring to a boil; cook and stir until thickened, 2-3 minutes. Set aside to cool slightly. Gently fold strawberries, raspberries, blackberries and lemon juice into the blueberry mixture. Preheat oven to 400°. On a lightly…