Real Food Encyclopedia | Onion

Onions are the true workhorses of the kitchen. They are the flavor cornerstone of just about every cuisine on this planet: crucial for cooking bases (like French mirepoix or Caribbean sofrito) and indispensable in curries, gravies, sauces, stews and stir-fries the world over. Without onions, many of our favorite dishes would be boring, indeed.

The vegetables we call simply “onions” (or “bulb onions,” or sometimes “dry onions”) are Allium cepa. But the genus Allium contains other, wild onion species, in addition to shallots, leeks, garlic, chives and some varieties of scallion and green onion.

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What to look for when buying onions

Choose onions that feel heavy for their size and are not sprouting. Avoid any mushy or brown spots — these can quickly cause the entire onion to rot.

Onions are divided into four major types based on their color and flavor:

• Yellow onions (sometimes called Spanish onions or brown onions) are great all-purpose onions and the most common variety seen in U.S. grocery stores. They have yellow-brown skin and a creamy-white interior.
• White onions are the most pungent, but also tend to be a bit more tender than the other types. As the name would suggest, both the flesh and the papery skin is a bright white.
• Red onions (sometimes called purple onions) have red-to-purple skin and white flesh with thin layers of red. They tend to be sweeter than either white or yellow onions and are often quite large.
• Sweet onions are valued for being less pungent than the other varieties, with a lower sulfur content. They are usually specially grown in certain parts of the country where the soil and climate produces a milder flavor. In addition to Vidalias, other notable varieties in the U.S. include Maui sweet onions and Walla Walla sweet onions.

Many of these are also available harvested young, without a fully developed bulb; you may see them called “fresh market onions.” They are sometimes also called “spring onions,” a term that is often used interchangeably with scallions and green onions.

Sustainability of onions

Onions are a fairly water-intensive commercial crop, which makes them less than ideal if sourced from drought-impacted areas. (Interestingly, onions that have been exposed to environmental stresses like drought tend to be far more pungent.) The good news is that you should be able to find local onions at just about any farmers’ market, year-round.

Pesticides

While chlorpyrifos, considered a staple pesticide in the conventional onion industry, was banned by the Environmental Protection Agency in 2021, the decision was overturned in late 2023 by a federal appeals court. Onions are very susceptible to nematodes and fungal diseases of the roots, so fumigants and fungicides are also common.

Still, these vegetables are solidly within the “Clean 15” from the Environmental Working Group’s 2023 Shopper’s Guide, in part because the outer layers are not typically eaten. If concerned, choose certified organic or locally grown onions and talk to your local farmer about their growing practices.

Eating onions

Storing

Stored in a cool, dry place, onions keep for many, many months. (Keeping them in the dark is also good; exposure to light hastens sprouting.) Fresh market onions should be stored in the crisper drawer and used within a week.

Cooking

Your first question, we’re guessing: How do I stop crying? There are many proposed methods for minimizing this side-effect of chopping onions, some of them more superstitious than scientific. The most effective include freezing the onion for a few minutes first, cutting it under a vented hood, cutting it under running water or (yes) wearing goggles while you’re doing it. Using a very sharp knife is also crucial. To easily get the onion smell off your hands after you’re done, rub them on stainless steel.

Raw onions add a crunchy, potent punch to salads, sandwiches and dips. Cooked, they become rich and full of umami — especially if they are done low and slow until their sugars caramelize. Their intense flavor means they’re often either hidden in the background or used as a side or garnish, as in pungent chutneys or creamy dips.

Some dishes, though, are all about the onion: French onion soup, for example, or the French caramelized-onion flatbread called pissaladière. (Also great, though decidedly less French: the bloomin’ onion.) For more ideas, Saveur has compiled a list of 50 onion-centric recipes.

Preserving

Onions, both fresh and caramelized, freeze beautifully. They can also be made into jam (like this one with bacon) or quick pickles. Like with scallions, it’s also fairly easy to “preserve” onions by turning them into more onions — here’s a guide to growing onions from onion scraps.

Nutrition

Onions are mostly water, but are a fairly good source of fiber and Vitamin C, and also offer Vitamin B6, potassium, magnesium, manganese and calcium. Onions also contain antioxidants, and their sulfur compounds have been studied for their potential to inhibit the growth of cancer cells.

Top photo by Galvman2/Twenty20.