1. Cut fish into 5 cm (2 inch) pieces and sprinkle with lemon juice.
2. Grind ingredients from chillies to small onion to a paste. Thinly slice medium onions and shred ginger. Fry in ghee or oil for 4 minutes,
then put in spicy coconut paste and fry for 2 minutes. Add turmeric, sliced chillies and chopped coriander. Infuse tamarind in water, strain and add to pan. Bring to the boil, reduce heat and simmer for 15 minutes.
3. Add sliced fish and cook gently for about 6 minutes. Season to taste with salt and sugar. Serve at once.