- Wash and dry the fruit, then cut it into quarters. Squeeze out the juice, then set aside. Use a spoon to scrape the pulp, seeds and pith from the skins, then tie them up in a muslin bag and place it in a deep stainless-steel saucepan.
- Thinly slice the skins, then add them to the saucepan and sprinkle with the salt. Make the juice up to 4 litres with water, then pour over the prepared fruit. Bring to a simmer, then cook for 1 hour or until the skin is soft and tender. Remove from the heat. Pour into a bowl and leave for 24 hours.
- The next day, return the mixture to the saucepan. Squeeze in the liquid from the muslin bag, then discard the bag. Add the sugar to the saucepan, then bring to a rolling boil for 25 minutes, skimming off any surface froth, until the marmalade reaches setting point. Pour into sterilised jars, then seal immediately.