The *Right* Way to Caramelize Onions (2024)

While following a weeknight pork ragú recipe from a celebrity chef who shall remain nameless, I came across the following, offending phrase in the method: “Cook onions until caramelized, 25 to 30 minutes.”

It doesn’t seem to matter how many articles, books, or cooking shows try to set the record straight. Even the experts among us cling to the hope that it’s possible to caramelize onions in 20 or 30 minutes, when in reality it takes about an hour to do it properly.

Perhaps we’re loath to commit so much time to an ingredient that always plays a supporting rather than starring role in recipes (unless you count this beloved braised onion pasta). Or maybe we’re playing a little fast and loose with the term “caramelize,” which at its simplest means the browning that occurs when foods containing sugar are introduced to heat. Searing sliced onions in neutral oil over high heat will indeed soften and make them deliciously brown in places in as little as 10 minutes.

But these are not Caramelized onions with a capital C: that intoxicating, mahogany jam that lends sweetness and rich, savory depth to everything it touches. Caramelized onions are “an onion transformed,” as chef and award-winning cookbook author Tamar Adler describes them—and they’re only achieved with time, attention, and patience.

Onions contain an impressive amount of sugar: some 4.7 grams (1.2 teaspoons) per medium (roughly 110-gram) onion, according to the U.S. Department of Agriculture. As food scientist and author Harold McGee writes in On Food and Cooking: The Science and Lore of the Kitchen, onions store their energy in chains of fructose sugars. Cooking them slowly for a long time breaks down these structures, coaxing out their inherent sweetness. As moisture is released—fresh onions are nearly 90 percent water—and the onion’s natural sugars slowly heat up, they caramelize, while the onion simultaneously undergoes a chemical reaction known as Maillard browning. (An important distinction: Caramelization only requires the presence of sugar, while the Maillard reaction is a chemical reaction between amino acids and sugars.)

In my experience, it takes at least 45 minutes for the onions to start to really relent, melt, and deepen in color. But if someone asks, I usually round up to an hour—or better yet, as long as they can stand to be there, babysitting a slow-cooking heap of onions.

Adler sympathizes with the home cook’s hesitancy to devote so much time to such a mere component of a dish. “I found a kind of loophole in talking about how long it really takes to caramelize onions,” she says. “I wrote in my first book An Everlasting Meal: Cooking With Economy and Grace just about caramelizing onions—like, just doing that, rather than making it part of a larger dish. The way I approach it is, if you’re going to be a bear, be a grizzly bear—meaning if you’re going to take the time to caramelize onions, do enough so you have the ingredient around for a while.”

This brings me to Adler’s caramelized onion recipe from An Everlasting Meal. It’s one of my favorites because it’s simple, yet just finicky enough to demand my regular attention throughout the process. Most importantly, it confidently asserts that “this will take 45 minutes to an hour.” Here’s the method:

1. Cut off the tops of 8 to 10 onions, then cut them in half through their roots, then lengthwise into slices about a quarter-inch thick.
2. Warm 3 tablespoons each of butter and olive oil in a big pot. When the butter is melted, add the mountain of onions, a small pinch of sugar, a big pinch of salt, and stir well.
3. Cook the onions over medium-low heat, stirring occasionally. Add occasional sprinkles of water if the onions begin to stick, she continues. If they start to sizzle, lower the heat and cover the pot, then uncover it again when the cooking has slowed.

Adler tells me she prefers the biggest yellow onions she can find for this recipe to minimize peeling. She favors equal parts olive oil and butter—oil to keep the butter from burning, butter for its round flavor and the sheen it gives the onions. She doesn’t always add sugar, a variable she looks to more for boosting sweetness than encouraging caramelization. She likewise can’t give an exact measurement of water. “Adding a few drops at a time lets you understand the rate at which water evaporates,” she tells me. “It’s a little absorbing lesson.”

She hadn’t tried (much less heard of) the so-called baking soda hack, in which a few pinches purportedly speed up the caramelization process to a mind-boggling 13 minutes, according to the National Onion Association’s successful attempt. Adding baking soda makes the onions more alkaline, increasing the speed of the Maillard reaction so they brown more quickly. But it also imparts a chemical-like bitterness to the end result. Adler hasn’t tried caramelizing onions in the oven on moderate heat, either (another method I unearthed that seems to work reliably well, at the expense of up to several hours).

Instead, her straightforward technique calls us to the stove with the task of observing, learning, and reacting—stirring periodically, adjusting the heat, covering and uncovering the pan, and sprinkling in water droplets if the bottom of the pan starts to burn. We can almost hear her voice in our heads as we go, reassuring us that the whole mass will look “soggy and unconvincing” right up until the onions are ready.

When the onions do finally melt into that elusive golden jam, we can keep it on hand to transform fried rice, soup, scrambled eggs and even sliced toast with broiled Gruyère and a few magical spoonfuls. Adler’s favorite method of late involves adding caramelized onions and smashed raw garlic to yogurt, which she tosses with short pasta in a nod to manti, or lamb-filled dumplings in yogurt sauce.

Of course, we don’t have to worry about making any of that until tomorrow. Today is just for the onions.