1. Grind ginger and garlic to a fine paste.
2. Mix ginger-garlic paste with tamarind pulp, cumin powder, red chilli powder, turmeric powder, salt, rice flour and two tablespoons of oil.
3. Marinate prawns in this mixture for at least two hours, preferably in the refrigerator.
4. Heat the remaining oil in a pan, add the marinated prawns and cook for a minute on high heat.
5. Turns the prawns and cook for another minute.
6. Lower heat and cook for two to three minutes, turning the prawns occasionally to cook.
7. Drain on absorbent paper, sprinkle lemon juice and serve hot.