In a small saucepan mix the strawberries, white sugar, water and lemon juice. Bring it to a boil over medium heat and cook at a slow simmer (low) for 5 minutes.

In the meantime, stir the cornstarch and 2 tbsp of water in a small bowl and add this mixture to the cooked strawberries. Remove from the heat and add the vanilla extract. Stir well and let it cool completely before serving. This sauce can be stored in the fridge in an airtight bottle or container for up to one week.