Greek Lamb Salad

In a bowl, mix the zest, juice, rosemary, garlic, and oil. Add the lamb and turn to coat. Refrigerate for an hour or so. Preheat a grill or grill pan. Season the lamb with salt and grill over a high heat for 4 minutes on each side or until cooked to your liking. Remove from the heat and rest for 5 minutes. Meanwhile, in a small bowl, whisk the dressing ingredients together. In a medium serving bowl, mix the lettuce, spinach, tomato, cucumber, olives, and cheese and toss with the dressing. Slice the lamb across the grain and serve with the salad.