1. In a bowl, mix together the Patak's Tandoori Paste and yogurt.  Grate in the zest from one lemon, cut the zested lemon in half and add a squeeze of the juice to the bowl.  Cut the other lemon in half and set aside.  Stir in the prawns and leave to marinate for 30 minutes.
2. Meanwhile, prepare the salad.  Heat a non-stick frying pan and dry fry the mustard seeds for a few seconds until they start to pop in the pan.  Tip the seeds into a bowl and add the tomatoes, red onion and beetroot.  Season and toss well.  Set aside until ready to serve.
3. Pre-heat a barbeque or grill to a high setting.  Thread the marinated prawns onto eight skewers, spray with the oil and cook for 10 minutes or until the marinade has cooked and the prawns have turned pink and charred slightly.  Grill the halved lemons whilst the prawns are cooking.
4. Heat the rice as directed on the packet.  Spoon the beetroot and onion salad onto four plates and garnish with a few salad leaves.  Serve the skewered prawns with the cooked lemons and the rice.

Note:

If cooking on the barbeque, place the rack high above the coals to prevent the prawns from burning.