Pierce the tomatoes with a toothpick, pour boiling water for a few minutes, then place in cold water this will allow you to easily remove the skin.
At the bottom of the sterile jar, place a pinch or two of salt and citric acid on the tip of the knife. Cut the tomatoes into 2 or 4 parts, depending on the size and put them very tightly in a jar so that there are no gaps, tamp a little.
Cover the jars and place in a pan with water, sterilize the jars after boiling water for 40 minutes.
Roll up the cans, turn the lid down and cover with a blanket until it cools completely.