Cut lemon grass sticks and peel them.
Mix together tamarind paste, lemon juice, red chilli powder, salt, lemon rind and 1 tbsp oil in a bowl.
Slice the prawns from the centre and add to the tamarind marinade and mix well.
Arrange the prawns on the lemon grass sticks. Heat 2 tbsps oil in a non-stick pan.
Add ginger, carom seeds and cumin seeds and sauté.
Add spring onion bulbs and sauté for 1 minute. Add the prawns, mix well and cook till done.
When the prawns are cooked, add fresh coriander and spring onion greens and mix.
Transfer into a serving plate and serve hot.