Yellow onions have a deep flavor but not too strong, making them very versatile in cooking. The yellow onion is higher in sulphur than the white onion, which gives it a stronger, more complex flavor.
Selection and storage
Look for firm, unbruised onions that are heavy for their size. If you plan on using your bulb onions within a few weeks, they can be stored at cool room temperatures in a dark place.
Preparation and serving methods
Yellow onions are ideal for long-cooking in soups, stews and braises, and of course are sticky and delicious when caramelized.
French Onion Soup by Epicurious