In a medium saucepan, bring cranberries, sugar, water, orange zest, and salt to a boil over medium-high heat, stirring frequently, until sugar dissolves. Reduce heat to medium-low, and cook, stirring occasionally, until cranberries have burst, begin to break down, and mixture has thickened, 10 to 15 minutes. Remove from heat, and transfer to a heat-proof bowl. Let cool completely before using. Refrigerate in an airtight container for up to 3 days.