Meanwhile, drain thawed raspberries, reserving juice in 2-cup measuring cup. Set raspberries aside. Add enough water to juice to measure 1 1/4 cups. In 2-quart saucepan, mix granulated sugar and cornstarch. Gradually stir in juice mixture with whisk. Heat to boiling over medium-high heat, stirring occasionally, until thickened and bubbly. Remove from heat; transfer to medium bowl. Stir in lemon juice. Gently fold in reserved raspberries. Cover; refrigerate until chilled.