Clean and cut the fish into medium-sized pieces, then season lightly with salt and turmeric.
Blend grated coconut, dried red chilies, coriander seeds, garlic, cumin, turmeric, and tamarind into a smooth paste.
Heat oil in a pan and sauté chopped onions until soft.
Add the prepared spice paste and cook for 5–7 minutes until fragrant.
Pour in water or thin coconut milk and bring the curry to a gentle boil.
Add the fish pieces and simmer for 8–10 minutes until the fish is cooked through.
Garnish with fresh coriander leaves and serve hot with steamed rice.