In a medium saucepan, cook cranberries, sugar, and salt over medium-high heat, stirring constantly, until cranberries begin to burst and mixture is boiling. Reduce heat to low; stir in 2 tablespoons (30 grams) water, and simmer, stirring occasionally, until filling holds its shape when a spatula is dragged through, about 5 minutes. Transfer to a heatproof medium bowl, and let cool completely. Cover and refrigerate until chilled, about 1 hour.