Juice 2 whole lemons or limes and keep the juice, skins and pulp. Cut all the fruit you’re using into equal-sized chunks. Layer the lemon and lime pieces with 75g flaky sea salt in a sterilised 500g jar. Pour in the juice to cover the shells, adding a few tbsp boiled cooled water to top up if needed. Press down well to remove any trapped air. Seal, shake, then add more salt if needed as some dissolves into the juice.
Mature in the fridge for at least 1 month, shaking every day for the first week, then every few days after that. The preserved lemons and limes are ready when the white pith has turned translucent. Use only the rind part of the fruit when you cook.