Cut and clean the fishes. Add some salt to the fish while cleaning. Change the water 4 to 5 times while cleaning the fishes. Keep the cleaned fishes aside.
Soak the tamarind in little water and keep aside for 20 minutes.
Heat few drops of oil in a pan and add dry red chillies.
Roast the chillies for few minutes. Remove and keep aside.
Now, add coriander seeds, cumin seeds, mustard seeds,carom seeds, black pepper and fenugreek seeds.
Roast the spices till they turn aromatic.
Transfer the roasted spices alongwith roasted chillies to a mixer jar.
Add one chopped onion, garlic, soaked tamarind and turmeric powder.
Add little water and blend to a smooth paste. Keep this masala paste aside.
Take a clay pot and add 1 tbsp oil into it.
Heat the pot.
Add 1/2 onion (chopped).
Add curry leaves and saute for few seconds.
Now, add the masala paste.
Add salt as per taste.
Add little water and allow the curry to boil. Water should be added as per the desired consistency of the curry.
When the curry starts boiling, drop the fishes into the curry.
After adding the fishes, swirl the pot so that the fishes are coated well with the masala. Avoid using spoon/ladle to give a mix.
If using a spoon, you will have to gently move the fish pieces in the curry.
Cook covered for 8 to 10 minutes or until the fishes are cooked.
Serve hot with steamed rice.