Cut peel from grapefruits into 3/8“ strips leaving 1/4” white pith attached.
Place in a small saucepan; add cold water to cover
Bring to a boil, then drain; repeat twice
Bring peel, 1 cup sugar, and 1/2 cup water to a boil in same saucepan; reduce heat and simmer until peel is translucent, 15–20 minutes
Drain; transfer peel to a wire rack and let dry, 2–4 hours
Toss in more sugar