Marinate fish with 1 1/2 tsp red chilly powder, 1/4 tsp turmeric powder and salt as required. Keep aside for 15 minutes. Then fry both sides in 2 tbsp hot coconut oil. Keep it aside and chop onion, tomato and green chilly.
Heat oil in the same pan and add ginger garlic paste and saute till raw smell goes off.
Add finely chopped onion and salt as required (or shallots), Fry well.
When onion gets fried, add sliced tomatoes, green chillies and curry leaves. Then add red chilly powder, turmeric powder and fry till tomatoes become mushy.
Take half masala from the pan and place it in a banana leaf.
Place fried ayala on the top of masala. Cover fish with remaining masala and cover all the sides of fish with the banana leaf.