Try this cilantro-scented sauce when beautifully fresh tomatoes and peppers are in season.
2poundsfresh plum tomatoes (if you have access to a farmers’ market, look for heirloom varieties; I’ve particularly enjoyed a deep-flavored, juicy yellow plum tomato)
1½cups chopped onions (scant ½pound)
1½cups diced sweet red peppers (look for the long, narrow, thin-fleshed frying peppers, such as Cubanelle, or, even better, local heirloom varieties; if unavailable, substitute finely diced red or yellow bell peppers; or add alittle finely chopped thin-fleshed mildly hot red pepper, like Hungarian wax pepper)
Prepare the tomatoes. Bring a 6-quart saucepan of water to a boil. Add the tomatoes and cook for 60–90 seconds. Using tongs, transfer them one by one to a large bowl to cool slightly. Peel off the skins (they should come off quite easily). Cut off and discard the stem end of each tomato and chop the tomatoes coarsely.
Heat the 2tablespoons regular olive oil in a heavy 10- to 12-inch sauté pan or deep skillet. Add the onions and sauté, stirring occasionally, over medium heat until softened, 5–7 minutes. Add the peppers, raise the heat to moderately high, and sauté, scraping and stirring the vegetables, until the peppers are soft and slightly caramelized, 7–8 minutes. Add the tomatoes and salt and pepper to taste and continue cooking, taking care to stir and scrape the bottom of the pan so the vegetables don’t burn, until the tomatoes are very tender and melting. The exact time will vary depending on the juiciness of the tomatoes, but figure on 10–15 minutes. If you prefer a sauce with a smooth texture, puree it in the pan using an immersion blender, or transfer to a blender, food processor, or food mill to puree. (If you want to reuse this pan to fry the fish balls, transfer the sauce to a bowl, then clean out the pan thoroughly.) Before adding the fish balls to the sauce, rewarm the sauce gently in the pan and stir in the extra-virgin olive oil and lemon juice. After the fish balls are cooked, sprinkle them with the cilantro and allow them to cool in the sauce before refrigerating.