Grilling Potatoes or other veggies in foil meals the whole meal can be cooked outside.
Preheat grill. Fold and 24x12-inch piece of nonstick foil in half to make a double thickness of foil. In a medium bowl toss the potatoes with the oil, 1/4 tsp. salt, and pepper. Place the potatoes in the center of the foil. Bring up opposite edges of foil and seal with a double fold. Grill, covered, directly over medium heat for 20 to 25 minutes, turning once halfway through grilling.
In a medium bowl, combine the lamb, onion, cilantro, cumin, and 1/4 tsp. salt and pepper. Form into four 3/4-inch thick patties. Grill burgers for 10 to 12 minutes (160°F). Layer the burgers on buns with sliced tomatoes and arugula. Serve with the potatoes.