At 'The Taste of Mexico,' a celebration of Mexican cuisine held recently in Los Angeles, we tasted dishes from some of the city’s top Mexican restaurants. As we strolled from one booth to another and sampled the chefs’ specialties, it was clear that what made the dishes so distinctive and delicious was the sauces. Many of them were enriched with ground nuts–walnuts, cashews, almonds or peanuts.With well seasoned sauces, simply prepared dishes became fit for a fiesta. We tasted several kinds of ceviche, which is made of raw fish marinated in lime juice to “cook” it, seasoned with salt and mixed with chopped fresh chiles (hot peppers) and often with chopped tomato and onion. The halibut ceviche served by El Coraloense was especially enticing. It came with two sauces–lemon aioli (garlicky mayonnaise) and peanut-walnut sauce. Marie Curie, the owner of the restaurant, told us that she prepared the nut sauce by frying garlic, peanuts and walnuts in olive oil, adding small potent chiles and blending the mixture to a smooth sauce. For contrasting texture and easy serving, the ceviche was served on a crisp tostada, a fried corn tortilla sometimes used as a base for salads.With vegetarians in mind, another restaurant, Punto Cabras, presented a ceviche made of cauliflower instead of the usual seafood. It was topped with the familiar avocado sauce known as guacamole and two additional salsas--one of ground cashews and another of pineapple and habanero, a very hot chile.ROASTED TOMATO SAUCE This recipe for tomato sauce flavored with dried chiles and sweet red peppers is from “Latin American Street Foods.” The vegetables are roasted, blended and cooked with oil until thick and concentrated in flavor.Author Sandra Gutierrez notes that charring vegetables prior to making sauces gives simple ingredients a rich and exotic flavor. “Most cooks have been taught not to burn garlic, but in Latin cuisines, charring it is desired for depth of flavor. Because the garlic is roasted while it’s still unpeeled, it develops a smoky and sweet flavor without turning bitter...This sauce keeps in the refrigerator for up to four days. It also freezes well, although it will turn a bit watery, so after you thaw it, cook it over high heat for about 5 minutes. I love it on tacos and on tostadas, ladled over eggs, or stirred into soups.”Makes 3 cups12 plum tomatoes1 large sweet red pepper2 large garlic cloves, unpeeled1 1/2 cups roughly chopped onion3 semi-hot dried chiles, seeded and chopped1/4 cup vegetable oil Salt and freshly ground black pepper to tastePlace the tomatoes, red pepper and garlic in a dry skillet over high heat or on a hot grill. Turn them until their skins are charred and blackened, about 4 to 5 minutes. Remove the garlic and peel it. In a blender with a good motor, and working in batches, combine the charred vegetables, onions and chiles. Blend until smooth.In a large pot, heat the oil over medium-high heat. Pour the sauce into the hot oil so that it sizzles; stir vigorously until it stop splattering and continue stirring for 5 minutes. Reduce the heat and simmer the sauce for 30 minutes or until it has begun to thicken; season with salt and pepper. Allow it to cool and refrigerate until ready to use.EASY CILANTRO-HOT PEPPER AIOLIThis sauce is delicious served with grilled or baked fish and in salads and sandwiches. To make it kosher for serving with roasted chicken or turkey, use nondairy sour cream, or replace the sour cream by additional mayonnaise. Remove the seeds and ribs of the hot pepper if you prefer a sauce that is less pungent, or leave them in for more heat. You can keep this dressing in a covered container up to 1 day in the refrigerator.Makes about 1 1/4 cups2 large garlic cloves, peeled1 fresh jalapeno pepper or other fresh green hot pepper, cut in 4 pieces1/3 cup packed cilantro (fresh coriander) leaves, patted dry1/4 cup packed small parsley sprigs, patted drySalt and freshly ground pepper1 tablespoon strained fresh lime juice1 tablespoon olive oil3/4 cup mayonnaise1/2 cup sour cream or yogurtWith blade of food processor turning, drop garlic cloves, then hot pepper pieces, through feed tube and process until finely chopped. Add cilantro, parsley, and pinch of salt and process until finely chopped. Add lime juice and olive oil and process until thoroughly blended; scrape bottom and sides of processor container several times.Add mayonnaise and process until blended. Transfer to a bowl and stir in sour cream. Taste and adjust seasoning, adding ground pepper if desired. SPICY PEANUT OR CASHEW SAUCEThis recipe is from “Wild About Greens.” Author Nava Atlas wrote that this rich spicy sauce, which is flavored with tomatoes, green onions and garlic, is great on just about any greens. It’s also good with fish, eggs, potatoes, pasta- and-vegetable dishes, and fish or vegetable tacos. Based on peanut butter, this sauce is quick and easy to prepare.Makes about 1 cup1 tablespoon olive oil or vegetable oil2 garlic cloves, minced2 green onions, white and green parts, sliced2 medium tomatoes, diced1 fresh hot pepper, seeded and minced, or dried hot red pepper flakes to taste 1/2 cup natural-style chunky peanut butter or cashew butter1 tablespoon soy sauce, preferably reduced-sodium, or tamari1 teaspoon natural granulated sugarHeat the oil in a large skillet. Add the garlic and the white parts of the scallions, and sauté over medium-low heat until the garlic begins to turn golden. Add the tomatoes, chili pepper and green parts of the scallion. Cover and cook just until the tomatoes have softened, 2 to 3 minutes.Add the peanut butter, soy sauce and sugar. Once the peanut butter starts to soften from the heat, stir it into the tomato mixture and add a small amount of water, just enough to make this a medium-thick sauce. Serve hot.Faye Levy is the author of “Faye Levy’s International Chicken Cookbook” and of the award-winning “Classic Cooking Techniques.”Visitors to the festival were drawn to the smoking barbecue at the booth of Mexikosher, a casual kosher restaurant in Los Angeles, where tacos of grilled meat were being prepared. We opted for the fish tacos, made of crisp, tempura-fried sardine-size fish set on corn tortillas and served with fresh coriander and two tasty sauces-- a hot serrano chile aioli and an anis and jalapeno pepper aioli. Devin Weil of Mexikosher told us that their fish tacos are especially popular during the Nine Days, the period leading up to the fast of Tisha B’av, when many people abstain from meat. (For an easy Mexican flavored aioli, see recipe below.) Aioli wasn’t the only European sauce that found its way into the Mexican tacos. The chef of Duro made tacos filled with brandade, a creamy salt cod puree from southern France. They were topped with fresh greens and a roasted red pepper sauce--Spanish romesco, which traditionally is flavored with garlic and ground roasted almonds or other nuts.At the booth of La Casita Mexicana, there were crisp potato tacos served with a tomato sauce and a salsa made from hot dried chiles. These kinds of Mexican vegetable sauces are easy to prepare and give pizzazz to grilled meats, roast chicken and even boiled vegetables. Cooks make such sauces from raw, simmered, roasted or grilled vegetables. Roasted tomato sauce is the favorite topping of author Sandra Gutierrez for Mexican grilled beef tacos because it enhances the smoky flavors of the grill. (See recipe below.) To prepare the beef, Gutierrez, who wrote “Latin American Street Foods,” marinates steaks with orange and lemon juice, onion and bay leaves for several hours, and sprinkles them with cumin, garlic powder, dried oregano and thyme before grilling them. She serves the sliced meat in corn tortillas and tops it with shredded lettuce and with the roasted tomato sauce. Gutierrez notes that in Mexico the steak is also accompanied by chopped onions and fresh coriander, and often by an additional avocado salsa as well. At the festival, a striking display of tacos coated with three different colored sauces caught our attention. Our friend, Barbara Hansen, author of “Mexican Cookery,” pointed out that these sauces were moles. These Mexican sauces feature chiles, aromatic vegetables, spices and often nuts or seeds that simmer at length with meat. To prepare green mole, for example, Hansen makes a sauce base of cooked green husk tomatoes blended with roasted fresh green chiles, fresh coriander, parsley, onion and garlic. She then sautés ground toasted pumpkin seeds and cooks them with the sauce base, meat, meat broth and cumin. Red mole, which is equally complex, contains tomatoes and dried chiles, while dark mole is flavored with chocolate.A sauce that was new to us was the sweet, red sauce in the dish called chicken coloradito at the booth of Guelaguetza restaurant. When we asked the busy man serving the chicken how it was made, he said, smiling, that it has peanuts and bananas, and 48 additional ingredients.