For The Best Melt-In-Your-Mouth Caramelized Onions, Choose This Variety

Caramelized onions add a rich balance of sweet-yet-savory flavor to many dishes, from a classic French onion soup to a warm onion dip or a Gruyére grilled cheese. While the caramelization process takes a while (unless you use this quick steaming technique), it's always worth it. The first step is choosing the right onions — there's technically no wrong onion here, but there are more onion varieties than you think. For the best flavor profile, though, use yellow onions. They're the United States' most common onion variety and are sometimes called Spanish onions.

When onions are cooked, moisture is released and sugar breaks down. The longer the onions sit on the heat, the more water and sugar is released. This results in the onions softening and, ultimately, browning. Think of the way sugar turns to caramel as it heats; that's essentially what's happening with the onions' sugars. With the texture and visual change comes a flavor change, bringing out onions' natural sweetness while creating a melt-in-your-mouth feel.

Yellow onions are the goldilocks of onions, in a sense. They have less sugar than red onions, but they're not quite as sharp and pungent as a white onion. Yellow onions have a little of both, which is why they develop the perfect profile when caramelized — just enough sweetness, but you don't fully lose that bite that makes an onion taste like an onion.

Yellow onions impart the most balanced flavor, but how long you caramelize yellow onions also makes a difference. Essentially, the longer you let them sit, the deeper that flavor gets because the sugars break down more. For a savory French onion soup, you want the onions light brown; the broth itself builds a ton of flavor thanks to ingredients such as wine and Worcestershire sauce, so the onions should complement rather than compete with that broth.

For a burger, where the onions need to stand up against rich, fatty beef, cook yellow onions until they reach a deep mahogany color, or a borderline-crispy brown — but you don't want the onions to burn. These are the richest in flavor, but it also takes the longest to achieve this color. As a general rule, onions take at least 45 minutes to caramelize, but can easily go over an hour depending on factors such as the heat level, the width and type of pan — we recommend using cast iron — the thickness of the onion slices, and how often you deglazing the pan.