Melt the butter in a 10" nonstick skillet over high heat. Add the onions, peppers, garlic, and the Fajita Magic. Cook until brown, stirring occasionally, about 10 minutes. Add the garlic and corn flour. Stir well, then add the ground turkey. Gently fold the vegetables into the meat, and break up the meat as you fold. Continue to cook, stirring occasionally, until all the meat is cooked through, about 8 to 10 minutes. Add the cilantro and fold in.
Fill each taco shell with 1/4 cup of the meat mixture. Topped with lettuce, tomatoes, and cheese. Serve immediately.