Place tomatoes and chilies in a pan about 10 by 15 inches. Broil about 2 inches from heat, turning as needed, until vegetables are charred on all sides, 6 to 8 minutes. Let stand until cool enough to touch.
Pull off and discard skin of tomatoes and chilies. Coarsely dice tomatoes. Remove seeds from chilies for less heat. Finely chop chilies. Mix tomatoes and chilies; add salt to taste.