This is my version of marinated peppers. There are no fixed quantities, and one can experiment many changes. The peppers can be kept for a while in the refrigerator. Somehow, the roasted or cooked pepper I try in supermarkets tend to taste awful. This recipe will give quite a different result. The key things are: a lot of olive oil, and a lot of cooking.
If you know of a good way to take the skin off the peppers, use that.
I simply take the skin off when I take the peppers out of the oven.
You can leave the skin on anyway. If you use the method of
burning the skin, do remove completely the burnt part. Unlike
when preparing grilled stuff, the burnt part will taste
very bitter when cooked.
Cut the peppers into three or four pieces, wash them and take off the seeds and the white filaments inside. Put the pieces in a large pan in the oven, with some olive oil (in addition to the cup you'll use to fry the onion) and a little water on the bottom, and I bake them uncovered in the oven (350) for a long time, stirring them often, until they are soft enough that the skin can be taken out (depending on the oven it may even take one hour).
Meanwhile, prepare the soffritto. Chop the onion in small pieces. Fry it in the oil (until golden brown, approx 10-15 minutes, but it depends on the temperature. Incidentally, you should not cook the olive oil at a high temperature because it has a low smoke point). A non-stick pan is very useful; you must stir very often anyway to avoid burning. During the last couple of minutes, add the garlic cloves and fry them with the onion. I use whole cloves of garlic, which gives a much milder flavor. If you cut the garlic in small pieces, the flavor will be more intense. In this case, use only 3-4 cloves. Do not burn or overfry the garlic, because the flavor will be extremely bitter and unpleasant. If that happens, there's no way to save it, so just throw away the soffritto and prepare a new batch. When the soffritto is ready, add the capers, all the flavorings, and the tomatoes. Keep frying it for 10 minutes or so, stirring often to avoid burning. Then switch off. In the sauce, I use capers under salt, which are more difficult to find. But capers under vinegar are also ok. If you use capers under salt, you have to soak and drain them first.
When the peppers are tender and the skin comes off easily, take them out of the oven, and take the skin off. (since they are hot, you may want to cool them down a little with cold water). Then put the peppers in a large pan with the soffritto, and keep frying them. Fry until all the water has evaporated and the peppers are very tender. Mix often to avoid burning (a non-stick pan is very helpful). When ready, pour the peppers and the sauce in a container, jar, etc, and cool. Do not serve immediately but let them sit for a few hours at least. When cold, you can store them in a refrigerator for up to one week.
You can serve them at room temperature, or slightly warmed in a microwave. They are perfect with Italian or French bread (for instance baguettes), so serve them with these types of bread. You can also make a sandwich this way, but remember that the peppers are very oily, and the oil will drip and stain if you're not careful.