I learned this simple method from Claudia Roden. You can also use limes or Seville oranges.
Scrub the fruit well, and slice or cut into wedges. Arrange on a tray, and freeze overnight in a freezer or in the ice-making compartment of a refrigerator. Put the frozen fruit in a colander set over a bowl. Salt generously and leave to drain for 1–2 hours. As the fruit thaws out, it will become soft and limp, and the pith will no longer be bitter. Layer the slices or wedges in a glass jar, sprinkling with a little paprika between each layer. Cover with a good-quality olive, nut or grapeseed oil, and close the lid. The pickle will be ready in 2–3 days.
© 1995 Frances Bissell. All rights reserved.