Remove skins of kiwifruit. Cut lengthwise and remove central core and the area close to it containing most seeds. Weigh fruit to 500grams. Mash with a potato masher. Microwave fruit and lemonjuice in a large bowl until fruit boils vigorously (6-8 minutes). Stir in the sugar, dissolving it as much as possible. Cook for about 8 minutes, or until jam sets. Pour into prepared jars and seal.
