Prepare the fish
Pat the fish pieces dry and season them lightly with salt, black pepper, and turmeric. Set aside while preparing the stew base.
Sauté the onion and garlic
Heat the oil in a large pot over medium heat. Add the chopped onion and cook until softened and lightly golden. Add the garlic and turmeric, then sauté for another minute until fragrant.
Cook the fresh herbs
Add the chopped cilantro and fenugreek. Cook the herbs over medium-low heat for several minutes, stirring occasionally, until they become darker and aromatic. Avoid overcooking the fenugreek, as it can make the stew bitter.
Add tamarind and spices
Stir in the tamarind pulp or paste, black pepper, and red chili pepper. Add the water and mix well. Bring the stew base to a gentle simmer and cook for about 10–15 minutes so the flavors can develop.
Add the fish
Gently place the seasoned fish pieces into the simmering stew. Cover the pot and cook over low to medium-low heat for about 10-15 minutes, or until the fish is cooked through and tender. Avoid stirring too much to prevent the fish from breaking apart.
Adjust and serve
Taste the stew and adjust the salt, tamarind, and chili according to your preference. Simmer for a few more minutes if needed, then serve hot with Persian steamed rice.