Over the past 5,000 years, nearly every world cuisine has embraced the onion. Its rich, savory flavor lends depth to cooked foods. When raw, it adds a pleasant bite to salads and sandwiches. But the onion does much more than season dishes.
These underground bulbs contain potassium, fiber, and folate, as well as the flavonoid quercetin, which helps eliminate free radicals that may contribute to eye degeneration, the aging process, heart disease, and cancer.
While it's true that nearly all onions share similar health benefits, it's a whole different story when it comes to their use in the kitchen. Onions are typically divided into two camps -- sweet and storage (aka dried) -- but even within these categories, each type has its own culinary characteristics. To make it easy, we've broken down a handful, highlighting what makes them stand apart -- and how to relish every bite.
What: Reddish purple in color with thick, crunchy flesh, red onions are more pungent than other sweet onions -- but still mild enough to eat raw. While Italian reds are generally available year-round, connoisseurs say the best arrive from Italy in midsummer; California-grown versions come into season from April to August.
How: When cooked, red onions become watery and lose their color. Raw, they add punch to salsas, salads, and sandwiches. For a tropical treat, slice them thin and toss with mango dressed with lime juice, olive oil, and salt. Or dice and add to guacamole.
What: Oval in shape with a deep golden skin, the white flesh of this onion boasts a crisp, juicy flavor. The best time to buy this member of the Allium family is in the fall, though it stores well. Milk-white Bermudas, which no longer come from the island but from Texas and Mexico, are a good substitute.
How: Spanish onions are a kitchen workhorse, adding depth to tomato sauce, paella, and omelets. Despite their strong flavor, these onions still shine raw, especially atop a beef or turkey burger.
What: When the crusaders brought them back to Europe from the Middle East in the 12th century, shallots were proclaimed a "valuable treasure." No wonder. These small copper-skinned bulbs have a milder (some would say more refined) flavor.
How: Wonderful roasted with olive oil, salt, and a drizzle of balsamic vinegar, shallots also make a splash when sauteed and tossed with braised greens or raw in vinaigrette. One drawback: Shallots can be tricky to peel. To loosen the skins, place these onions in boiling water for 30 seconds, then plunge them into ice water. Drain and peel.
What: Sometimes called green onions, scallions are actually baby onions picked before a large bulb has formed. Don't confuse them with spring onions, which have larger bulbs and make a showing only in May and June -- or with the thicker, longer leeks, a relative of both onions and garlic.
How: The fresh, mild flavor of scallions makes them the ultimate garnish. They're particularly appropriate for Asian dishes like steamed bass with ginger or soy-glazed salmon. Also try scattering a few over brown rice and sauteed mushrooms.
What: The most popular variety in the United States, these storage onions with a tan papery skin have a strong flavor, much more so than their white cousins. Tearjerker alert: When cut, these beauties cause eyes to water. For fewer tears, run the bulb under cold water while peeling and use a sharp knife.
How: When any recipe calls for simply "an onion," use a yellow globe. Too sharp for most to eat raw, the flavor becomes layered and sweet when cooked. Their high sugar content allows these onions to caramelize, making them the perfect partner for grilled steak or an egg-white omelet.
What: To earn the name "Vidalia," an onion must come from one of 20 counties in Georgia. The low sulfur content in the soil makes this light-brown-skinned onion especially sweet. At their best from late April until mid-June, these onions typically appear in stores through the autumn. When you can't find one, look for a Walla Walla from Washington or a Hawaiian Maui instead.
How: The mild, sweet flavor of Vidalias makes them an excellent choice to serve raw, especially to spice up a boring tuna salad. They're also tasty grilled on a vegetable or chicken kebab.