We love to eat grapefruit, but usually toss the peel away. For this candied citrus peel recipe, look for organic grapefruit so you don't have to worry about insecticides or fungicides.
Using a vegetable peeler, remove all the zest from each grapefruit, being careful to remove just the outer layer and leave the white pith behind. Cut the strips of zest into pieces 2 to 3 inches long and 1/4 inch wide.
Combine the zest and 2 cups water in a small saucepan; bring just to a boil. Drain and rinse under cold water.
Return the zest to the pan along with the remaining 2/3 cup water and 1/3 cup sugar. Bring to a boil, stirring to dissolve the sugar. Cook until the liquid is reduced and very syrupy, about 5 minutes. Remove from heat.
Spread the remaining 1/3 cup sugar in a shallow dish. Using a fork, transfer the zest to the sugar (leave any syrup in the pan). Using two forks, tease the zest apart and toss in the sugar until each strip is complete coated. Transfer to a large clean plate or platter and let stand until dry.
To make ahead: Store airtight for up to 1 week or refrigerate for up to 1 month.