For each heaping cup of tomatoes, use level cup full of sugar. Squeeze about half of juice and seeds from tomatoes; leave skin on. Put sugar, tomatoes, and 1/2 lemon sliced for every four cups sugar and tomatoes in pan and cook over medium heat. Cook 20-25 minutes until bubbling. Cool a little to taste if set. Cook until set. skim off foam. Put in jars. Seal.