Some make their peperonata by first cooking the onion and tomatoes into a sauce, then adding the peppers at the end, while others cook the onion and peppers first, finishing with the tomatoes. Roman writer Ada Boni has a recipe from her 1929 cookbook "Il Talismano della Felicità" (“The Talisman of Happiness,” which was published in a very abridged version in English as "The Talisman") where the peppers, onions, and peeled and seeded tomatoes all go into the pot at the same time and are doused with some olive oil and salt, placed on a very low heat, and covered for an hour so that the whole thing slowly, slowly stews together. Right at the end, a glass of vinegar goes over the top and it's ready.
I love the ease of her method: Pop it all in and let it cook slowly and steadily on its own. And because I love the sweetness of peppers too much, I don't add vinegar. But feel free to adjust as you please. —Emiko
Score a cross in the bottoms of the tomatoes and blanch for about 30 seconds in boiling water. Immediately place them in a bowl of cool water until they're cool enough to manage and it's easy to peel off the skins. Chop into quarters, remove seeds, and dice the flesh. Set aside.
Slice peppers into thin strips a few inches long.
In a deep skillet, heat a few tablespoons of olive oil over low heat and add the onion, the peppers, and tomatoes with a good pinch of salt and some black pepper. Cover and let cook, stirring and checking occasionally, until the peppers have melted down into very soft, silky stew and the tomatoes have broken down into a thick sauce, about 1 hour. If needed, splash with water every now and then.
Remove from the heat, scattering with basil, and serve at room temperature.
The Australian-Japanese cookbook author has lived in Florence (where a visit to a cheese farm once inspired her to start a food blog) for over 10 years with her Tuscan sommelier husband and two kids. Her third cookbook, Tortellini at Midnight, is out now.