Heat 3 Tbsp oil in Flat pan or Kadai.
Add the fish pieces and fry each side for 2 minutes.
Remove the fish and keep aside.
Add the remaining oil to the Flat pan or Kadai.
Add mustard seeds and wait for it to splutter.
Add the small and big onions and fry on high heat for a few minutes till the onions are translucent (transparent).
Add ginger-garlic paste and fry for about 5 minutes or till the raw smell goes away.
Add the green chillies and fry for a minute.
Add coriander powder, chilly powders, turmeric powder. Fry for another 2 minutes.
Add tomatoes and tamarind pulp. Mix well on fry for another 3 minutes.
Reduce the heat and cover the Pan/Kadai and let it cook till the oil separates, about 8-10 minutes.
Add jeera powder, curry leaves, salt and water. Let it boil well.
Add the fried fish, reduce the heat and let it boil for 10-15 minutes.
Add the fenugreek powder and mix gently without breaking the fish. Increase the heat and let it boil for a minute.
Add the coriander leaves and turn off the heat.
Serve with hot rice or chapati!