Marinate Fish slices with turmeric powder, 1 tsp of salt, lemon juice for 15-30 minutes.you can add 1 tsp of chilli powder which is optional.
Heat oil in a flat based kadai. Add finely chopped Onions and fry at medium flame. Cover for a minute and fry again. Add curry leaves and green chillies.
Add chopped tomato. Keep the flame low to medium.
Cook for 3-4 minutes till they are mushy.You can cover with a lid in between for a minute.
Add red chilli powder and fry at low flame.
After a minute put fish slices like this.
Add tamarind pulp to 1 cup of water . Mix and add this to fish. Add 1 more cup of water. Let it cook for 5 minutes at medium to high flame.
Make a paste of garlic , coriander seed, cumin seed and fenugreek seed with little water. Add this to curry. Cover and Cook for another 5 minutes.
Add fresh coriander leaves, adjust salt at this point. Add more water if you need. Cover and cook at medium flame for 5 minutes. It’s ready.