I decided to grow a lot of "roma" paste tomatoes so I could do some canning this year, as well as having plenty for fresh salsa. I've learned that it's not worth all the work of canning unless I have a big quantity to do at once. After reviewing recipes, I decided to "put up" marinara sauce instead of just canning whole tomatoes. Canning whole tomatoes called for boiling-blanching-peeling, and I figured that would be nearly as much work as making the sauce! I had purchased a food mill (Roma brand) two years ago and I've used it for wonderful tomato juice, apple sauce, pear sauce, grape juice, salsa, and other great foods. This year, I am using it for the tomato sauce and it has made my work so much easier... with delicious results. And you can also freeze the marinara sauce... if you don't just eat it all fresh!
To the bowl of pure tomato puree, I add chopped garlic, loads of chopped fresh basil, chopped onion (all from my garden too), salt, and some of my jalapeno powder. (You can add other ingredients too, but I try to stick with recipes when hot water bath canning so I don't alter the pH. And adding meat requires pressure canning.) Then it all gets "cooked down" to about half the original volume, to thicken the sauce, which I do over medium low heat with the pot uncovered so the moisture can evaporate. It's so hot here that I hate to heat up the house with hot pots on the kitchen stove, so I use a portable gas cooking unit set up on the big porch. Great view of the mountains, so it's not too shabby! Works out great when I am doing a lot of canning too, using the outdoor dining table as my work station.
Caution: canning is LOTS of work! When you figure all your time and what you get out of it, you can only justify it with the fact that you are using wonderful freshly harvested food and your own good ingredients.
So try making your own tomato sauce. We'll be enjoying ours next winter when there are no fresh tomatoes around.