Wash the prawns thoroughly, apply a little salt and set aside.
Heat one teaspoon oil in a pan and lightly sauté coriander seeds, cumin seeds, black peppercorns, fenugreek seeds and whole dry red chillies. Grind them with coconut, half the onion, garlic, turmeric powder and tamarind pulp to a fine paste.
Heat the remaining oil in another pan, add the remaining onion and sauté till transluscent. Add the ground paste and continue to sauté for two to three minutes. Add prawns and stir. Add two cups of water and bring the mixture to a boil.
Cover and cook on medium heat till the prawns are done.
Serve hot with steamed rice.