Marinate the fish pieces with pepper powder, turmeric powder, salt & lemon juice. Keep it for half an hour.
Shallow fry the marinated fish for just 2-3 minutes. Heat oil in a pan. Add crushed ginger garlic & green chillies.
Add chopped onions. Once the onion becomes soft add chopped tomato,turmeric powder,pepper powder and curry leaves and saute till the tomato goes soft.
Add thin coconut milk and let it boil. Add the fried fish pieces and salt to this and boil for further 5 minutes. Add thick coconut milk and boil for another two minutes.