Place hibiscus flowers in the center of a large piece of cheesecloth or clean muslin. Tie tightly into a bundle with food-safe twine.
Cook Sauce
In a saucepan, combine cranberries, water, sugar, and lime juice and nestle hibiscus bundle within the liquid.
Bring to a simmer, stirring occasionally and keeping hibiscus bundle submerged, and boil for 10–15 minutes or until cranberries are burst and liquid is thickened.
Remove hibiscus bundle, squeezing out as much liquid as possible, then discard.
Notes
Sauce can be made up to 3 days ahead of time and refrigerated in a jar or airtight container.