Also known as brown onions for the yellow-brown papery peel, these are usually the cheapest at the grocery and are available all year. They’re both sweet and bold (onion-y?), and should be cooked unless you want some intense onion-tasting food and extra-intense onion-smelling breath. They have the highest sulfur content of all the onions, which gives it that potent onion flavor when raw.
Stick with these for things like French onion soup, caramelized onions, stews, and shish kabobs.