Marinate the lamb by laying it in a shallow container and covering with 3 tablespoons of extra virgin olive oil thyme, cumin, garlic and lemon zest. Mix to coat the lamb. Cover and refrigerate.
Pick the leaves from the parsley and mint and discard the stems. Add them to a bowl with the tomatoes and onion and mix. Mix the yoghurt with the remaining extra virgin olive oil, lemon juice, sumac and paprika flakes with a good pinch of salt and pepper.
Heat the grill or BBQ. Cook the lamb for 3 minutes on each side or browned all over. Allow to rest.
Place the salad on a tray. Dress with the yoghurt dressing. Slice the lamb. Place on the salad. Season. Serve.