Wash prawns and rub in salt and turmeric. Set aside. Heat oil, add sliced onion and fry unitl yellow. Add all the other spices and fry 2-3 minutes and then add prawns. Mix prawns together with the spices and the add either grated coconut, ground coconut or using a little water, squeezed out coconut milk. If you are using coconut milk, add half cup of hot water, if using grated or ground coconut add 1 cup hot water. Cover and cook over slow fire until prawns are tender and a very thick gravy remains.