Lyonnaise sauce is a classic French sauce made with butter, onions, and white wine. There are a few synonymous variations of this flavorful sauce such as Sauce Lyonnaise, Sauce à l'Oignon, and Onion Sauce. This rich sauce has a sweet and tangy taste that complements many dishes, especially meat dishes like steaks and chops. The sauce is often eaten with roasted or grilled meat and pairs well with a side of mashed potatoes or roasted vegetables. Whether you call it Lyonnaise Sauce or Onion Sauce, it is a must-try for anyone who loves savory, rich flavors.