Tomatoes are usually preserved in three different forms, each of which has its particular uses. First there are the ordinary tinned or bottled whole tomatoes, pomodori pelati, which contain a high percentage of liquid and are best used for dishes that require a tomato base but need a long cooking time. Secondly there is the puree, passato di pomodoro, which is a much thicker reduction of tomatoes, sometimes flavoured with celery, onion, carrot and basil, then called pomaruola or conserva. This is ideal for sauces which need a rich body of tomato. Thirdly there is the tomato concentrate, concentrato di pomodoro, which is the tomato reduced to a very strong paste and flavour and is useful for colour and flavour in a dish where bulk tomato is not required. Silvana usually uses a puree of tomatoes for her sauces so she prefers to make a rich thick conserva or passato of tomatoes. She also likes to utilize her fresh basil while she has it and preserves her tomatoes with a base of the flavoursome carrot, celery and onion.
At the very end of August Silvana can be seen in the orto filling her twig baskets with ripe whole tomatoes. She is very careful to select perfect specimens with no trace of damage or decay. The kitchen table is spread with the lovely fruit and at the end of the table is a bunch of green basil and a few onions, the yellow variety, a carrot or so and some ribs of celery.
To make the conserva Silvana cuts the tomatoes into four and puts the pieces into a very large pan together with some salt, pieces of carrot, celery and a roughly chopped onion. Then she leaves the pan to simmer very gently on a low flame until the tomatoes dissolve into a soft red mass. When the tomatoes have reduced, the vegetables softened and the excess liquid has cooked away, she forces the mixture through a fine sieve to eliminate the skins and seeds (or you can use a blender, if you don't mind the seeds). The puree is left overnight in a large pottery bowl.
Around Naples, where the southern gardeners and cooks really prize their tomatoes, they put their tomato conserve in large shallow pottery bowls called scaffliria. The conserve is reduced to a very thick and jam-like consistency and on the firm surface they spread a thick layer of coarse sea salt which covers the tomato completely. The salt attracts moisture from the tomatoes to make a dense concentrate. Then the bowls are left out in the sun for several days. The resultingconservahas a wonderful consistency and a rich, sweet flavour.
Silvana does not follow this southern custom but she does add salt to aid the conservation process. Then comes the time to put the thick scarlet conserve into pots. Silvana uses glass jars with patent metal tops like jam-pot lids. The jars are thoroughly scalded and dried, then she spoons in the conserve to the top of the pot. Some conserves and pickles are put under a layer of olive oil but in these types of jars the oil eats away the linings of the lids. Instead Silvana puts a layer of ground black pepper right over the surface of the conserve (we screw the lids on tightly and boil the full jars for about 25 minutes). When the time comes to open the jars Silvana breaks the vacuum with a coin, listening carefully for the sound of the breaking seal to be sure that the jar has been properly closed. Badly sealed tomatoes can provoke serious stomach upsets.