The stew gets its sour edge from tamarind paste rather than the lime, pomegranate, or vinegar souring agents used almost everywhere else in Iranian cooking.
Fresh fish is simmered in a thick, herb-heavy sauce built from cilantro, garlic, tamarind paste, turmeric, and chili, until the sauce turns deep green-brown and the fish falls apart. It's ladled over rice at riverside eateries and market stalls in Ahvaz and Abadan.