Strawberry Filling:
Blend the strawberries, water and sugar in a blender until smooth. In a small bowl, whisk together lemon juice and cornstarch for 1 minute; add to the strawberry mixture and continue whisking for 30 secs. Strain the mixture into a medium saucepan. Simmer over medium heat until the mixture starts to boil. Stir frequently and cook a few more minutes or until it thickens. Strain again and let cool to room temperature.