Combine together ground turmeric, ground black pepper and lemon juice in a large bowl. Season with salt. Tip in the fish pieces and toss well to coat. Cover and refrigerate for 30 minutes in the refrigerator.
Heat oil in a frying pan over medium-high heat. Add fish pieces. Cook until both sides get a light brown color. Cook in batches if needed.
Fish Molee:
Heat oil in a large pan (preferably a claypot) over medium-high heat. Splutter mustard seeds. Tip in the onions. Cook, stirring occasionally, for 1-2 minutes or until softened.
Add ginger and garlic. Cook, stirring, for 2 minutes or until aromatic. Add green chili and a sprig of curry leaves. Saute for a minute. Add tomatoes, and fry for another 2-3 minutes or until they start to break down.
Stir in ground turmeric, ground fenugreek, ground coriander and red chilli powder. Saute, stirring, for 1-2 minutes or until aromatic. Season with salt.
Stir in thin coconut milk. Carefully place the fried fish pieces in the curry. Simmer for 5-6 minutes. Add thick coconut milk. Simmer for 2-3 minutes. Scatter over the rest of the curry leaves. Pour in white vinegar and heat through.
Garnish with curry leaves and serve with rice, appam, idiyappam, chapathi or bread.
Notes
-Use coconut oil for authentic taste. -I used pomfret in this recipe