Take a bowl add a fish pieces and marination ingredients in bowl and mix well. And keep a aside for 2 hours.
Take pan heat a pan. Add a oil in pan.
Add chopped onions in pan and fry until a golden brown color of chopped onions.
Add a chopped tomatoes in pan. And fry for 3-4minutes.
After that add a cashew nuts paste, red chili powder, fennel seeds(saunf), turmeric powder in pan and fry for 2-3 minutes.
Keep a pan aside for cooling the item in pan. After that grind the pan items in blender. Make it in smooth paste.
Take a another pan heat it. Add 1 tsp oil in pan and add a fish pieces and fry the fish pieces until the golden color of fish pieces in both side.
After fish pieces fry Take pan and Add a 1 tbsp oil in pan.
Add 1 tsp cumin(jeera ) in pan.
Add chopped onions, curry leaves and green chilies in pan and fry until the golden brown color of onion.
Add ginger-garlic paste in pan and fry until the raw smell.
After that add red chili powder and garam masala in pan mix well and fry for 2 minutes
Add ½ cup of water in pan for gravy. After gravy start a boiling keep boiling for 5-8 minutes in medium flame.
Add a fish pieces in pan and cook for 10-12 minutes for proper fish dish.
After 10 minutes fish curry is ready to eat.
You can also garnish with coriander leaves, mint leaves, etc.