Marinate the fish pieces with the ingredients under marinade for around 30 mts.
Heat around 2 tbsp coconut oil in a wide non-stick pan. Add the ginger, garlic, sliced onion and green chillies. Saute well at medium heat. When the onion turn golden, add the tomatoes and curry leaves.
When the tomatoes get mashed up, lower the heat and add the turmeric powder, chilly powder, coriander powder, pepper powder and fennel powder. Check for salt. Mix well and lay the marinated fish pieces on the masala.
Cover the pan with a lid and cook at low heat turning the fish pieces carefully in between. It will take around 30 – 40 mts. Coat the fish pieces with the onion masala and cook for another 10 mts. (You can cook the fish at medium heat, if you feel that the fish will not get properly cooked at low heat. Saute in between, so that the masala wont get burnt but take care not to break the fish pieces.)