In a small saucepan, over medium heat, combine the blueberries, sugar, water, cornstarch, and lemon juice. Cook, while stirring frequently, until all the blueberries have burst and the mixture has thickened - about 10 minutes cook time.
1/2 fresh blueberries, 1/4 cup granulated sugar, 2 tablespoons water, 2 teaspoons cornstarch, 2 teaspoons fresh lemon juice