For the French toast: Whisk together the eggs, cinnamon and milk. Heat a large cast-iron skillet and add the butter. Dip the bread in the egg mixture and turn to coat. Place in the pan and cook in batches for 4 to 5 minutes per side until all the ingredients are used. Whisk together the sugar and cinnamon and sprinkle on top of French toast.
For the spaghetti frittata: Preheat oven to 350 degrees. Heat a 10-inch cast-iron skillet over medium heat and add the oil. Whisk together the milk, eggs, Parmesan, salt and pepper. Stir in the pasta. Pour pasta mixture into skillet and cook for about 5 to 6 minutes. Place in the oven and cook an additional 10 minutes.