Spread the scallops in a single layer in a glass baking dish. Remove long strips of peel from 1 orange and 3 limes with a paring knife, being careful not to remove the white pith; set the peels aside. Juice the peeled fruit and the remaining oranges and limes to make 1 cup of each juice; pour into a bowl. Add the celery, onion, tomatoes, scallions, olive oil, 1/2 cup ice water, and pepper to taste; pour over the scallops. Cover and refrigerate until the scallops are opaque, 1 to 4 hours.
Meanwhile, make the candied citrus: Place the orange and lime peels in a saucepan of water; bring to a boil and cook for 1 minute, then drain. Boil in fresh water 2 more times; drain and set aside. Combine the sugar and 1 cup water in the saucepan; bring to a boil, stirring to dissolve the sugar. Reduce the heat and return the citrus peels to the pan; simmer for 45 minutes. Transfer the peels with a slotted spoon to a rack, reserving the syrup; let the peels cool, then slice into 1/4-inch pieces.
Drain the excess marinade from the ceviche. Add the cilantro and candied citrus peels, season with salt and toss. Transfer to a serving bowl and lightly drizzle with some of the reserved orange-lime syrup. Serve on endive leaves or with toasted bread, if desired.
Winning Recipe: Read about the Chairman's Citrus Challenge
Photograph by Kate Sears
Recipe courtesy Jeff Ockerman for Food Network Magazine