Heat grill. In medium bowl, combine ground beef, onion, curry powder and salt; mix well. Shape mixture into four 6-inch sausage-shaped rolls. Flatten each to 2-inch width. Place a 12-inch metal skewer through center of each roll.
In medium bowl, combine yogurt, cucumber and lemon peel; blend well. Set aside.
When ready to grill, place skewered meat rolls on gas grill over medium heat or on charcoal grill 4 to 6 inches from medium coals. Cook 9 to 12 minutes or until meat rolls are thoroughly cooked, turning once.
Remove skewers; place meat rolls in pita bread halves. Top each with lettuce, tomato and yogurt sauce.