Prepare the vegetables and sliced lamb according to the instructions above.
Sprinkle lamb slices with salt and pepper and place in a nonstick pan with sliced onions over medium heat. Cook gently, turning the meat and onion mixture often, until heated through and the onions are starting to soften.
Make the yogurt sauce: Combine yogurt, garlic, cumin, lemon juice, salt, and pepper. Set aside.
To assemble, heat naan bread in a skillet on both sides until warm and pliable. Place some lamb and onion mixture next, and then top with tomatoes, mint, and parsley. Drizzle with yogurt sauce.
Serve the flatbreads with carrot sticks, hummus, and lemonade.