Lemon is the citrus fruit preserved in salt and used in Moroccan tagines.
Preserved lemons are made by packing lemons with salt and allowing them to cure in their own juice for weeks or months. The process softens the peel and changes its flavor, producing a salty, intensely lemony ingredient. In Moroccan cooking, preserved lemon is particularly associated with chicken tagine and is also used in salads, sauces, and vegetable dishes.
Cooks commonly rinse the preserved lemon before use and may discard the pulp while slicing the softened peel into a dish. The peel is valued because its texture and flavor become quite different from those of fresh lemon.
Preserved lemons are not the same as lemon zest added at the end of cooking. Their salt-cured character contributes both seasoning and citrus aroma. Similar preservation methods exist elsewhere, but Moroccan cuisine made this ingredient especially recognizable internationally.