Romaine lettuce, originating from the Vega de Aranjuez, San Martín de la Vega, and Ciempozuelos, is also known as cos lettuce. This type of vegetable features an elongated head characterized by its lanceolate leaves, which are slightly thinner than those of iceberg lettuce. In Spain, it is referred to as 'mule ear.' Its texture is crispy, and it has a slightly acidic taste, making it a versatile ingredient for various recipes. Nutritionally, romaine lettuce is low in calories, providing only 17 kcal per 100 grams. It consists of 94.61% water, making it ideal for staying hydrated. Additionally, it contributes carbohydrates, fiber, and protein, making it a healthy addition to a daily diet. To preserve its freshness longer, it is advisable to carefully separate the leaves, wash them, dry them well, and store them in a closed container in the fridge. This type of lettuce is perfect for preparing salads, especially the famous Caesar salad, which may include ingredients such as chicken, croutons, and parmesan cheese. Adding a dressing made from ingredients like anchovies and mustard creates a delicious and nutritious dish.