will make about 6, 300 ml jars
1 kg sugar
Cut the plums in half and take out the seed, grate the lemons and the apples including the skin and the pips and put in a heavy based pot. Bring fruit to the boil with 2 cups of water, simmer until fruit cooked and soft. Puree fruit and add sugar bring back to boil and simmer until it reaches setting point. (to check setting point place a little on saucer in fridge when its cold it should be set).
This simple jam recipe is suitable for berries and apricots too.