I take about a dozen fresh tomatoes dip them into boiling water briefly and then peel the skins off. Chop them up into pieces, then place them into a saucepan with a cup, cup and a half of water, cover and let simmer with seasonings until they reach the right consistency. You may want to remove the lid and simmer more to condense it further.
You can also puree it at the end if you want a smoother sauce, in a food processor. A blender may add too much air and then you would need to cook it again, stirring to get the air back out. I personally do not mind the seeds being in there..it is hard to see them with the other herbs...but you could remove them before hand.
One batch could be made with Italian seasoning, another with a Mexican, Mediterranin, these freeze well for 6 months or more.