To peel a tomato, first lightly bruise the flesh under the skin in order to loosen it. Holding the tomato in one hand and a paring knife in the other, gently drag the paring knife, held at an angle, from the stem to the blossom end. Do this all the way around the tomato as if you were peeling an apple.
To remove the skin, flip the tomato over and cut a slash in the blossom end. Then, grab the edge of the skin at the slit and with your thumb and the paring knife and pull the skin away. It should all come off in a few pulls. Core the tomato and put it in a bowl while you peel the rest.
To seed the tomatoes, halve them horizontally (through the equator). Working over a sieve set over a bowl, barely squeeze each tomato half (as if juicing an orange) and give it a gentle shake. If necessary, use the index finger of your free hand to gently prod the seeds out of each cavity. When all the tomatoes are seeded, chop them coarsely and place them in a bowl. Use a spatula or ladle to stir the contents of the sieve, continuing to stir and press against the sieve until all the juice has passed into the bowl and all that remains in the sieve is the seeds. Add the juice to the tomatoes.
After reading this description, you may decide that you prefer a puréed/smooth sauce. But it is much more difficult to describe than it is to do. Furthermore, in the time it takes you to peel and seed your tomatoes your onions will have had plenty of time to cook. And this is important, because sufficiently cooking the onions is, to me at least, one of the secrets of a fine tomato sauce.
When you begin cooking the onions, set them over moderate heat. This will encourage them to start to give up their juices. If you are using farmers' market onions, they should be fresh and juicy this time of year. I get mine from the same farmer who sells me the tomatoes. After a few minutes the onions will be stewing in their own juices. As they cook the juices will evaporate and the onions will then be cooking in just the oil. The heat should be turned down at this point so the onions can continue to cook slowly without caramelizing. The onions will take on a straw yellow color as they continue to cook, but they should not brown. When the onions are done they will have shrunk quite a bit in volume and they will be very soft. Don't try and shorten this process. The final sauce shouldn't contain crunchy bits of onion. And the long, gentle cooking process will draw out the inherent sweetness of the onions—a good thing for a tomato sauce.
As for the other flavorings, the original recipe contains an abundance of garlic and I have not changed this. The garlic cooks slowly with the onions and then in the sauce so it mellows considerably by the time the sauce is finished. But you could of course cut down on the garlic to suit your palate.
Winter savory, a frequently-used herb in Provençal cookery, is Lulu Peyraud's herb of choice for the tomato sauce. The book mentions that it grows outside her back door. I too have winter savory growing on my patio, but for some reason I always reach for the thyme instead.
You could also add bay leaf. Other possible herbs include oregano, marjoram or rosemary. I think these last three have a much stronger voice than thyme, so I probably wouldn't use them for a sauce destined for the freezer. You can always add one of these herbs when you thaw the sauce to tailor it to whatever you are making.
When you make your tomato sauce, choose a pan that is wider than it is tall. You want the sauce to be able to reduce as it cooks and a wide surface area will allow it to do this more rapidly. Cook the sauce at a brisk simmer.
When the sauce begins to thicken, reduce the heat a bit so that the sauce won't scorch. Stir the sauce occasionally and use a heat proof spatula to scrape the sides of the pan so that any sauce building up there can be stirred back into the simmering sauce. I also use the spatula to smash the tomatoes against the bottom and sides of the pan as they break down.
3 to 4 T. olive oil
2 medium onions, finely diced (about 10 to 12 oz.)
8 to 10 cloves garlic, minced
4 to 5 lbs. vine ripened tomatoes, peeled, seeded (juices reserved) and chopped
Several sprigs of fresh thyme or winter savory, tied with a string
In a wide sauce pan, sweat the onion in the olive oil over medium heat. When the onions begin to soften (after about 10 minutes) add the garlic along with a pinch of salt. Reduce the heat and continue to cook until the onions are meltingly tender and have taken on a pale yellow cast (but are not caramelized). This will take about 30 to 45 minutes.
Add the tomatoes and the thyme. Increase the heat and bring to a brisk simmer. Continue to simmer, stirring occasionally and scraping down the sides of the pan until the sauce is thickened—about an hour. Remove the thyme. Taste and correct the seasoning.
If you like, purée the sauce. An immersion blender is best for this, since it will leave the sauce with some texture. If you don't have an immersion blender, transfer half of the sauce to a blender or food processor to purée and combine this the purée with the sauce still in the pan—again, to achieve a final sauce with a little texture. I think the sauce is nicest when it has not been puréed—the larger pieces of tomato will have broken down during the cooking process and the resulting sauce will have just the right amount of chunkiness. Makes 4 to 5 cups.
The final picture above is of a sauce that was half puréed. Here is a picture of one that has not been puréed:
(Recipe adapted from Lulu's Provençal Table by Richard Olney)