The Moroccan term citron beldi (or l'hamd beldi) translates to "traditional lemon." It refers to specific varieties of lemon which are grown in Morocco and favored in traditional cooking, including the small doqq lemons (Citrus limonum Risso var. pusilla R), which grow predominantly in the Taroudant region outside of Agadir and boussera lemons (Citrus limon (L.) Burm), which are also called limonette de Marrakesh.
The latter is a type of Mediterranean sweet lemon which, according to Paris-based cookbook author David Lebovitz, may mistakenly be sold as "bergamot" in France. Limonettes de Marrakesh and bergamots, however, are very different fruits, as true bergamot (Citrus bergamia Risso) is larger in size and much less palatable. Because their juice is so bitter, bergamots are appreciated mostly for their aromatic essential oil. Nonetheless, "bergamot" appears to be a term wrongly associated with the Moroccan boussera lemon.
How Are Citrus Beldi Different From Other Lemons?
Both doqq and boussera types of citron beldi are distinguished by their orange-yellow color at maturity, pleasantly fragrant skin and unique shape―they're smaller and rounder than some other cultivated lemon varieties, and the bouserra has a flat apex and an especially prominent nipple. While citrons beldis have general culinary value in Moroccan kitchens, they're most notably used to make and, or Moroccan preserved lemons. The distinctively petite doqq lemon, as noted by Moroccan cuisine expert Paula Wolfert in her book The Food of Morocco, is considered the crème de la crème for this purpose, due to its thinner skin and fragrant aroma.
More About Preserved Lemons
Preserved lemons, simply put, are lemons which have been preserved in salt and their own juices. They're an essential ingredient in Moroccan cooking and show up in a great many dishes, where they impart a uniquely pungent and salty lemon flavor. Some cooks may be tempted to try using a regular, fresh lemon instead, but it's a poor substitute as it lacks the mellowed essence which is unique to preserved lemons.
Fortunately, making your own preserved lemons is quite easy and simply requires patience, as the lemons will need to cure for a month or longer before they can be used. If you're outside of Morocco and can't find the sweet Mediterranean or Moroccan variety, then try using Eureka, Meyer or other lemon variety of your choosing.
You can also buy preserved lemons online. Be sure to select ones which have been brined in only salt and water; additional spices or herbs are not normally added in traditional Moroccan cooking.