Adapted from Anne Quatrano's Summerland: Recipes for Celebrating With Southern Hospitality (Rizzoli).
Lightly oil a 1-quart nonreactive mold or a few smaller molds. Combine cranberries, sugar, zest, orange juice, lemon juice, and 1 cup water in a large saucepan over high heat and bring to a boil. Reduce heat to medium and cook, stirring occasionally, until cranberries burst and are completely softened, 12 to 15 minutes. Pass mixture through a fine sieve into a bowl, gently pressing on solids (pressing too hard will make the mixture cloudy). Skim any foam from surface; cover to keep warm.
Sprinkle gelatin over 1/2 cup water in a bowl; let soften 1 minute. Stir gelatin mixture into warm cranberry mixture until gelatin is completely dissolved. Pour mixture into mold and refrigerate until set, at least 8 hours.
Dip top of mold into a bowl of hot water 30 seconds, then run a paring knife around edge to loosen. Place a serving platter on bottom of mold; quickly invert platter and mold together. Tap to release; remove mold. (If gelatin doesnâ??t release easily, return to hot water for a few seconds.)
Once set, the mold can be covered with plastic wrap and stored in the refrigerator up to three days.