Remove and clean the tail of the prawns. Place the prawns in a bowl and squeeze half the lemon over it and let it stand for 10 – 15 minutes, turning occasionally. When ready to assemble with the salad discard the lemon juice.
In a large bowl combine the cleaned salad cut up to desired pieces size, the prawns, and the feta cheese. Cut the tomatoes and remove all the seeds and white part and add to bowl. In another small bowl prepare the vinaigrette with the oil, vinegar and salt.
When nicely blended add to the salad bowl. Mix well. Squeeze at the last minute the remainder half of lemon over the salad.