Combine Karo syrup, margarine, lemon rind, and cinnamon in a small saucepan. Bring just to boil.
Arrange apple halves in a single layer, cut side up, in a 12x8x2-inch baking dish. Spoon syrup mixture over apples.
Bake in a 350 degree oven about 50 minutes or until apples are fork-tender. Baste frequently during baking. Cool. Makes 6 servings.