Onion Vatha Kuzhambu is a tangy and spicy South Indian curry made with onions, tamarind, and a blend of aromatic spices. It has a thick and flavorful gravy, making it a perfect accompaniment to rice. The onions are cooked until soft and then simmered in a tangy tamarind sauce. This dish is easy to make and can be stored in the refrigerator for a few days.