Start with rubbing some salt on fish fillets. I have used readymade fillets which were already cleaned. If you prefer to cut the fish on your own then first clean it throughly, fillet it and apply some salt. Keep these fish fillets aside.
Take a pan over medium heat and add oil into it. Once oil is hot enough turn heat to medium-low. Add onion seeds into it and let it crackle for few seconds.
Meanwhile, finely chop onion and tomatoes.
Next tip in chopped onions into the pan and stir continuously.
Once onions starts to change its colour, add spice powders one after the other. If required add little hot water so that spices won't get burnt. Mix everything together and then tip in ginger garlic paste. Combine everything and add chopped tomatoes into the pan.
Mix it thoroughly so that tomatoes are coated with spice mixture. Add hot water and cover the pan. Let everything cook over medium heat for 5-7 minutes or until tomatoes start to soften.
Make a thick paste or adjust the consistency as required. I like to keep a thick paste.
Season with some salt.
Time to add seasoned fish into the pan. I have cut fillet into small pieces. Slowly transfer your fish fillets into the pan.
Gently coat fish with the paste. If required add some hot water.
Cover the pan and let it cook over medium heat for 5 minutes then simmer for another 5 minutes (or until fish is cooked). While curry is on simmer; add chilli if using. Test taste and add some salt if required.
Turn off the heat and garnish with lots of fresh coriander.
Fish curry is ready to serve.