Rinse and core tomatoes and cut into about 1/4-inch dice; put the tomatoes with their juices into a bowl. Rinse and stem the jalapeño; shake out seeds and cut out the veins. Finely chop the chili. Add it to the bowl, along with the onion, cilantro, and 3 tablespoons lime juice. Stir gently to mix, and add more lime juice and salt and pepper to taste.