Rinse the ripe tomatoes. Heat in a covered pan with a little salt and water. When soft, rub through a hair or nylon sieve. Reheat, and fill quickly into hot preserving jars. Fasten and process, using a pan with a false bottom.
To process: Cover the jars with hot water, raise to boiling-point, and boil for 10 min. Remove from water. Test for seal next day.