Canh chua or cá nấu is a Vietnamese sour soup indigenous to the Mekong Delta region of Southern Vietnam . It is typically made with fish from the Mekong River Delta, pineapple, tomatoes, and bean sprouts, in a tamarind-flavored broth. It is garnished with the lemony-scented herb ngò ôm, caramelized garlic, and chopped scallions, as well as other herbs, according to the specific variety of canh chua; these other herbs may include rau răm, ngò gai, and rau quế . It can be served alone, with white rice, or with rice vermicelli. Variations can include prawns, squid, spare ribs, fish cakes and quail eggs.
The sour taste of the soup comes from tamarind, which is mixed with a small amount of hot water; the mixture is then stirred for a few moments to release all the essence, and the liquid (minus the tamarind seeds and other solids, which are discarded) is then added to the soup.
When made in style of a hot pot, canh chua is called lẩu canh chua.