Remove stems from strawberries. Place strawberries and water in a blender and puree the mixture.
Use a sieve to strain the mixture into a saucepan - let it strain on its own without pushing it through.
Add sugar and lemon juice to the strawberry mixture. Bring the mixture to a boil and skim the foam off the top. Lower the heat, and simmer for 15 minutes.
Remove from the heat and stir in the vanilla paste.
Allow to cool before using. Pour into a container (I like glass bottles) and store in the refrigerator.