Wash ripe tomatoes thoroughly
Remove stems and any damaged spots
Cut tomatoes into quarters
Blanch tomatoes in boiling water for 30 to 60 seconds
Transfer tomatoes to ice water
Peel off the skins
Remove seeds if desired
Blend or process the tomatoes until smooth
Strain through a sieve for a finer puree
Pour the puree into a saucepan
Simmer over low heat until thickened to desired consistency
Stir occasionally to prevent sticking
Cool completely
Store in a clean container in the refrigerator or freezer