Can I un-seal canned tomato sauce, and re-seal after further cooking?
We make a lot of sauces every year. I wouldn't try to do it over. If you know what its lacking just add it to your sauce as you use it. Sometimes bland sauce can be a good thing and offers you an open door to add what you want. If you're missing some flavors you like or don't have enough of it just add it for now with seasonings. Make a mental or written note for next year to try and zero in on what exactly you want to produce.