Wash and core the tomatoes
Score a small X on the bottom of each tomato
Blanch the tomatoes in boiling water for 30 to 60 seconds
Transfer the tomatoes to ice water
Peel off the skins
Chop the tomatoes into chunks
Melt butter in a pot over medium heat
Add chopped onion and celery if desired
Cook until softened
Add the chopped tomatoes
Add salt, pepper, and a pinch of sugar
Add a little water if needed
Simmer uncovered for 20 to 30 minutes
Stir occasionally
Cook until the tomatoes are soft and slightly thickened
Serve warm