In saucepan combine sugar, cornstarch and salt; stir in water and lemon juice and mix well. Add blueberries. Cook over medium heat, stirring often, until mixture is slightly thickened and bubbly. Cook and stir 2 minutes more.
Transfer to bowl; cool. Serve at room temperature. Or chill, covered, up to 2 days. If chilled, let stand at room temperature 30 minutes before serving. Makes 3 cups.