Last week, Cup of Jo reader Kris asked if we could talk about different kinds of onions and the best ones to use for which recipes — and I’m so glad she did. I usually have some combination of the six main varieties you see above, but use them interchangeably when I have to, and I’ve always wondered what the food police would say about this. The answer? It’s not a big deal, but, not surprisingly, there are definitely specific recipes that call for specific onions for very specific reasons.

Here’s a rundown for you…

Yellow Onion
When a recipe calls for an onion, this is usually the kind it means. It’s the workhorse you should pick up by the sackful at the supermarket (they can last 2 to 3 months when stored in a cool, dry place) and with its strong flavor (which mellows out when cooked) a dependable aromatic base for soups, stews, stocks, roasts and braises. They are the premier onion for caramelizing.
Start with: Pasta with Yogurt and Caramelized Onions, Cauliflower and Onion Gratin, Broccoli Soup

Red Onion
Red onions are slightly more biting than yellow onions — some say “spicier” — but still sweet, which is why they are commonly used raw. (You can soak them in water for a few minutes to reduce the bite, if you prefer.) Their vibrant hue also makes them popular for visual flourishes, sliced onto sandwiches and burgers; pickled into a versatile garnish; or minced and tossed in salads.
Start with: Pickled Onions (scroll all the way down), Kale Salad

White Onion
This is a sweeter, more mild onion than red or yellow, and therefore best deployed raw and in small doses, like in pico de gallo, salsas, and guacamole. (They’re popular in Latin and Central American cuisine.) I’m embarrassed to admit that I only recently started adding them (in very thin shaves) to my guacamole instead of red onions, and I’m now addicted to the little bursts of crispy sweetness.
Start with: Guacamole, Fish Tacos with Pico de Gallo

Shallot
Probably the most versatile of the bunch, these smallish bulbs are more delicately flavored than most onions, and delicious minced into salad dressings, roasted whole, or fried and frizzled to be sprinkled on soups and stews.
Start with: Ottolenghi’s Miso Butter Onions; or add finely minced shallots to any of these dressings

Scallions
Also known as green onions, you can’t put these slender alliums into any one box. They are mild, crispy and pretty, making them a go-to garnish onion. (My stir-fry dishes, green salads, grain bowls and chilled soups feel naked without them.) But also, they’re just as dependable as a flavor builder when cooked (into a stir-fry with their besties ginger and garlic) or when charred (and used as a topping for pizzas and creamy soups) or baked into biscuits or scones.
Recipe: Arugula Salad with Chicken and Mint, White Pizza with Scallions and Egg, Cheddar Biscuits

Leeks
Most recipes will call for leeks the way they call for regular onions — as a flavor builder — but they are more delicate, and, in my opinion, both pretty enough to be a stand-alone dish and distinct enough to earn headline status in recipe names. Of all the onions in this round-up, these are the ones I have the most fun with, the only one I would categorize as “muse” when I’m developing recipes. Only downside: They can be a pain to clean.
Recipe: Potato-Leek Soup, Beans and Buttered Leeks, Simple Braised Leeks

Sweet Onions
These aren’t necessarily sweeter than regular onions, but they contain less sulfur than most so are not nearly as pungent. Think of them as more of the main show than a supporting character — in other words, think of them for onion rings. Walla Walla, Vidalia, Maui are all varieites of sweet onions, named for the regions where they grow.
Recipe: Onion Rings

Thanks for the question, Kris!

P.S. Lentil salad and creative ways to upgrade roast vegetables.