1 1/3 c. grapefruit juice
1 c. sugar
1 pre-baked empty pie shell
1/3 c. water
1/2 c. cornstarch

Juice may be canned but I sometimes take time to pull skins and veins off fresh grapefruit and liquify in the blender, very time-consuming.

Pour all ingredients (except the pie shell) into a pan on top of the stove. Stir until the mixture starts to thicken up. Pour into the pie shell. After the pie cools, before serving, top with whip topping. OPTION: Might want to put grapefruit pieces on top of the pie.