Brought to Calabria 2,000 years ago by the Phoenicians, red onions are typical of the Tropea area, between Vibo Valentia and Capo Vaticano. Other prized and lesser-known "red" varieties can be found in Zerli, in Liguria; in Castelnuovo Scrivia, in Piedmont (the violet variety); in Lombardy, with the ancient Palanzo variety; and in Puglia, in Acquaviva delle Fonti.

In Tropea, the harvest still takes place by hand and begins at the end of June, continuing throughout July. Traditionally, red onions are left to dry and plaited into "braids", which is how they are kept until the next harvest. The local microclimate and soil quality make them sweet, white on the inside and red-violet on the outside. They are rich in flavour and extra-nutritional properties. Eaten raw, they are very pleasant on the palate — sweeter and more aromatic than white and golden onions. And it is always when eaten raw that their beneficial active compounds perform at their best.

All varieties of onion — white, golden or red — have numerous virtues: they reduce the body's insulin demand, are antibacterial, laxative when cooked and diuretic when raw, antibiotic, useful against flu and colds, anti-anaemic, anti-sclerotic, anti-stress and anti-cancer.

The properties of Tropea red onions

Red onions, however, have something extra: it is quercetin (the flavonoid that colours their skin red), a precious antioxidant that stimulates the immune system and which, in synergy with the vitamin C found in the vegetable, helps protect capillaries and connective tissue, with an anti-couperose effect. Try adding them to seasonal salads, flavoured with anise and fennel seeds and paired with a good sheep's cheese: they are easy to digest, and so fragrant that they lend themselves — without any taboo about bad breath — to a candlelit dinner. Not bad for a vegetable that contains no less than the active ingredient of one of the world's most famous pills, "viagra".

Quite so: the Italo-Argentine scientist Pasquale Potenza, a lecturer in biochemistry at the University of Buenos Aires, has discovered that the Tropea red onion contains "nitrous oxide", the pharmacological substance found in the famous "love pill".