Chettinad Vengaya Kosu, also known as Onion Kosu, is a popular South Indian dish from the Chettinad region. It is a spicy and flavorful curry made with onions, tomatoes, and a blend of aromatic spices. The dish is known for its rich and tangy taste, making it a perfect accompaniment for rice or roti. The onions are cooked until they are soft and caramelized, giving the curry a sweet and savory flavor. This dish is a must-try for those who enjoy spicy and aromatic South Indian cuisine.