1 medium cucumber—peeled, seeded and thinly sliced
1/3 cup pitted black olives
1/3 cup crumbled feta cheese
In a food processor, combine the lemon juice with the lemon zest, rosemary, garlic and 1 teaspoon of pepper and pulse to blend. With the machine on, slowly pour in 1 tablespoon of the olive oil until a paste forms. Spread 1 tablespoon of the lemon paste all over the lamb and refrigerate for 10 minutes.
Light a grill or preheat a grill pan. Season the lamb with salt and grill over a medium-high fire for 8 minutes, turning once, until an instant-read thermometer inserted in the thickest part of the meat registers 125° to 130° for medium rare. Transfer the lamb to a platter and let rest for 5 minutes.
Meanwhile, in a medium bowl, toss the tomatoes with the cucumber, olives and feta cheese. In a small bowl, whisk the remaining lemon paste with the remaining 1/4 cup of olive oil and season with salt and pepper. Toss the salad with the dressing and mound on plates. Carve the lamb across the grain into 1-inch slices and serve with the salad.