The simplest salsa of all—ripe tomatoes, seeded and diced, mixed with sweet onions, cilantro, lime, a pinch of salt, and fresh hot chiles. If you prefer, omit the hot chiles; then you have salsa fresca. For a more picante salsa, increase the chiles. Good tomatoes are a must for this salsa, which is a classic, served on all types of tacos. I prefer to use roma or plum-type tomatoes that are ripe but firm. When tomatoes are out of season, or not great, try making salsa quemada with them instead.