Combine peel and water to cover in small, heavy nonaluminum pot. Boil gently until peel is tender—about 40 minutes. Drain liquid and measure; there should be a little less than 1 cup. If there is more, boil a few minutes to reduce. Discard solids.
Return liquid to pot with lemon and orange juice and sugar. Bring to a boil, stirring. Boil until mixture reaches j