1. Rinse shrimps under cold running water, remove heads. Using scissors or a small knife, cut the shell on the back of each shrimp down to the tail. Part the meat and remove the dark intestinal muscle. This is a must if you are cooking large king prawns. It is also better to cut the shell of medium-sized shrimp - then they marinate more evenly. 2. Put the shrimp in a bowl, pour over the marinade. Cover with cling film and leave for 1 hour. 3. Wash the tomatoes and lemons. Cut the tomatoes in half, cut the lemons into 1 cm thick circles. Arrange on the grill along with the shrimps and fry until tender.