Etrog

The etrog (Citrus medica) is the ceremonial cultivar of the citron used in the Jewish autumn festival of Sukkot, where it is one of the "four species" waved together with palm, myrtle and willow. Botanically it is a citron — a large, thick-rinded, intensely fragrant yellow fruit that is mostly peel and pith over a little dry, acidic pulp — but its ritual role, its prized unblemished form and its afterlife as candied peel and jam give it a culinary and cultural identity distinct from the ordinary citron of the fruitcake tin.