Ok some more background. Tomatoes are a mix of Roma, Amish paste, pink girl, lemon boy, and a couple beefsteak varieties. All I were ripe. We typically chunk and freeze them during growing season then thaw and cook this time of year.

Wife's batch is pretty basic, olive oil, lots of garlic small dash of Italian season mix.

Mine is as above but I add onions, green pepper, and sweet basil.

Both batches were simmered about 24 hrs to reduce water content and thicken. Stirred often and not allowed to boil.

This isn't bitterness like a unripe tomato, more like a grapefruit effect.

We don't like sweet sauce so sugar is a last resort.

Also we added butter and lard. Potatoes gad come up in a search but not tried. Was potato raw or cooked?

Adding starch has crossed my mind as a possibility that wouldn't thin the sauce.