Combine garam masala, onion, garlic, ginger, oil, and red pepper in a medium mixing bowl. Stir in pork, working spice mixture into meat with fingers. Thread the meat onto metal skewers, leaving 1/4-inch between pieces; cover and refrigerate for 1 to 24 hours.
Place pork skewers in a lightly oiled rack of the grill directly over medium heat. Grill for 12 to 15 minutes or until juice run clear, turning once. Meanwhile, stir together yogurt and cilantro in a small serving dish. Cover and chill until serving.
To serve, use a fork to remove grilled pork cubes from skewers. Arrange a tray around yogurt mixture. Serve pork cubes with toothpicks. Makes 6 servings.