Strain the puree through a fine sieve to remove the seeds.
Add sugar and water to the puree.
Pour mixture to a small saucepan and whisk in the cornstarch.
Bring mixture to a boil and then turn heat to low and let simmer for 5 minutes, whisking continuously.
Remove sauce from heat, it will continue to thicken as it cools
Note: To freeze pour the sauce into single serving resealable containers and let it cool completely before putting the lid on. Store in the freezer until ready to use. Microwave for 15 - 30 seconds or until heated through and enjoy!