Pour sweet potato liquid into saucepan. Add brown sugar, margarine, lemon juice, vanilla and cinnamon, Bring above to boil. In a small amount of water blend cornstarch until smooth. Add to boiling liquid and stir constantly tuntil thick and clear looking. Grease dish. Place sweet potatoes in dish then pour liquid over them. Bake 350 degrees 30 to 40 minutes until brown and bubbly. Sinful but delic!!!!