Combine sugar and water (or orange juice) in a medium saucepan and bring to a boil, stirring until the sugar dissolves.
Add the cranberries, return to a boil, then reduce to a simmer. Cook 10 to 15 minutes, until the berries pop.
Stir in orange zest and a pinch of salt. Cool to room temperature, then refrigerate until fully set, at least a couple hours or overnight.
Taste once cooled and adjust sugar, salt, or orange juice as needed.
Notes
The sauce looks thin in the pot and thickens as it cools, so don't oversimmer chasing a thicker texture on the stove. Don't push much past 15 minutes of simmering.