Mash the ripe avocado, add lemon juice and blend. Peel, chop and drain the tomatoes. Add along with remaining ingredients to the avocado mixture; blend. Cover and chill. Serve over chicken enchiladas or as a sauce over any Mexican-style chicken, beef, or cheese dish. Also serve with tortilla chips as a dip. Can be kept in refrigerator up to 24 hours if covered very tightly.