Caramelized onions are the star of this dish, providing a sweet and savory flavor that is simply irresistible. To achieve the perfect caramelization, it's important to take your time and cook the onions low and slow. Start by thinly slicing the onions and sautéing them in butter or olive oil over low heat. Stir them occasionally to prevent burning and cook them until they turn a deep golden brown color, which can take around 30 to 40 minutes. This slow cooking process allows the natural sugars in the onions to caramelize, resulting in a rich, sweet flavor that will elevate your French Onion Pie to new heights.