A good cranberry relish can make or break Thanksgiving. This one, flavored by orange and grapefruit, is aromatic, sweet, and tart all at once.
Combine cranberries, sugar, orange juice, and both zests in a medium saucepan over medium heat, stirring until sugar is dissolved, about 5 minutes. ( depending on the cranberries you may need additional sugar)
Bring to a boil, stirring occasionally, then reduce heat to medium low and simmer until thickened and cranberries are beginning to fall apart, about 20 to 25 minutes. Spoon into a heatproof serving bowl.
Drain grapefruit segments, discarding any accumulated juices, and stir into cranberry sauce. Cool to room temperature, cover, and refrigerate until ready to serve. Serve cold or at room temperature.