Here diced heirloom tomatoes, onion, garlic, and chiles are broiled in the baking dish to make a ranchera sauce for the chicken breasts. It's a one-pan wonder to be served straight from the baking dish, along with a green salad or Humble Beans, and warm corn tortillas for scooping up the sauce.
Preheat the broiler. In a 13 x 9 x 2-inch flameproof baking dish, toss the tomatoes, onion, chopped cilantro, jalapenos, and garlic with 2 tablespoons of the oil. Season with salt. Broil for about 3 minutes, or until the vegetables begin to soften and char. Remove from the broiler and stir the vegetables.
In a medium bowl, sprinkle the chicken with salt and the remaining 1 teaspoon oil and toss to coat. Nestle the chicken into the tomato mixture and turn to coat. Broil for about 12 minutes, or until the chicken is cooked through and the sauce is bubbling and slightly charred on top.
Sprinkle the cheeses over the chicken. Broil for 2 to 3 minutes, or until the cheese melts and begins to brown. Sprinkle with the cilantro leaves and serve.