Though you can certainly buy preserved lemons, we prefer the rich, clean taste of homemade. This technique, adapted from Paula Wolfert's, brings a multidimensional freshness and a wonderfully distinct pungency to the lemons, which are as much a revelation in salads, soups, or even cocktails as they are alongside the grilled fish. There's no need to rinse them first, but do discard the pulp — only the rind is eaten with the grilled sardines.
Cooks' note:
Preserved lemons can be chilled, covered in their juices, up to 1 year.