Caramelized Onions for Pizza: The Slow Way and the Honest Cheat

Somewhere right now, a recipe is telling someone to cook onions until caramelized, about 5 minutes. Five minutes gets you onions that have been warned. It does not get you caramelized onions.

Real caramelized onions for pizza take about 45 minutes, and most of that is standing near a pan, not working. There are also two shortcuts with evidence behind them, and each one costs you something specific.

So I pulled the cook times from nine top-ranking recipes, read the journalist who put a stopwatch on this, and checked the USDA numbers on what an onion is made of. Here is the slow way, the cheat, and how to get either one onto a pizza.

Why Cook the Onions Before They Hit the Dough

Raw onion on pizza is a perfectly good topping. It is also a completely different ingredient from the sweet, soft, mahogany tangle people mean when they say caramelized.

The difference is water. USDA’s nutrient data for raw onions puts them at 89.1 percent water. A pound and a half of sliced onions is carrying about 21 ounces of it, which is more than two and a half cups.

Caramelizing drives that water off in a skillet instead of on top of your dough. So this pre-cook pays twice: deeper flavor, and one less cause of the soggy-topping problem.

It also earns a place among the homemade pizza toppings worth an hour of your weekend. Not sure which toppings need pre-cooking at all? Start there.

The Five-Minute Lie

I pulled nine of the top-ranking US recipes for caramelized onion pizza and wrote down how long each one says the onions take. Same vegetable, same goal, very different clocks.

The shortest and longest times differ by a factor of five or more. They can’t all be describing the same food, and they aren’t.

The person who settled this was Tom Scocca, who put a timer on it for a 2012 Slate piece on onion cook times. On high heat, his onions were scorching by minute 8, and at minute 11 he scraped out an inedible mess. On medium-high with close attention he got there in 28 minutes, after lowering the heat at minute 24 to avoid scorching.

His advice: give yourself 45 or 50 minutes on a moderate flame. The National Onion Association, a group with every reason to make onions sound easy, says truly caramelized onions take around 45 minutes, sometimes longer.

So the short recipes are not caramelizing. They are sauteing. Golden, softened onions after 8 minutes are a fine thing to put on a pizza. They are just not this.

What Is Happening in the Pan

Two things have to happen, in order, and the first one is boring.

First, the water leaves. BAKERpedia’s reference page on the Maillard reaction, the browning reaction between sugars and amino acids, gives its typical range as 150 to 160°C, or 302 to 320°F. A pan full of wet onions sits near the boiling point of water, 212°F. For the first stretch nothing browns, no matter how hard you stare at it.

Then the sugar goes to work. The same USDA data lists 4.24 grams of sugar in every 100 grams of raw onion, and about three quarters of it is glucose and fructose. Baking-science references rank those two as the fastest sugars to caramelize, with fructose starting at around 302°F.

This is why I skip the pinch of sugar some recipes add. That pound and a half of onions already holds about an ounce of its own.

Which Onion to Buy

Yellow. In Pizza Today’s rundown of onions for pizzerias, John Gutekanst of Avalanche Pizza in Athens, Ohio calls the yellow onion the workhorse of many kitchens. It caramelizes easily, he writes, and the flesh holds up in cooking.

• Red onions also caramelize easily, and the color fades to pink with heat.
• Sweet onions (Vidalia, Walla Walla, Texas) are great raw. Heated, they lose their onion flavor fastest.
• White onions are sharper, but they fall apart when cooked.

Buy by weight, not by count. USDA’s reference medium onion weighs 110 grams, a little under 4 ounces. One recipe I surveyed calls a pound and a half 2 medium onions, which makes each of those 12 ounces. The word medium is doing a lot of freelance work.

The Slow Way, Stage by Stage

The whole method in one breath: sliced onions, fat and salt over medium heat until they collapse, then medium-low and patience, with a splash of water whenever the pan bottom gets dark.

The clock matters less than the color. These stages follow the timeline Emma Christensen published at The Kitchn.

The Cheat: Two Shortcuts and What They Cost

Two shortcuts have real evidence behind them. Both lean on baking soda, and they produce different onions.

Cheat 1: Baking Soda From the Start (About 13 Minutes)

The National Onion Association tried the baking-soda shortcut with 1 pound of yellow onions, 2 tablespoons of butter and ⅛ teaspoon of baking soda over medium heat. They had soft, browned onions in about 13 minutes.

It works because the Maillard reaction speeds up as the pan gets less acidic. Chemist Martin Lersch ran a side-by-side onion experiment on his food-science site Khymos, and his baking-soda batch browned much faster and tasted remarkably sweet and caramel-like.

The fee is texture. Lersch notes the same alkalinity breaks down the onion’s cell walls, so the strands slump. The onion growers describe the result as almost like an onion jam, and they say plainly it is not the method to pick if you want onions with some bite on a pizza.

I think that undersells it. Onion jam is a terrific pizza base. Spread it thin where the sauce would go and build a white pie on top. Respect the ceiling, though: the growers cap it at ¼ teaspoon per pound, and Lersch found too much leaves the onions mushy and wet.

Cheat 2: The Steam Start (About 30 Minutes)

Cook’s Illustrated’s quicker caramelized onions, by Lan Lam, starts with water. Three pounds of onions go into a 12-inch nonstick skillet with ¾ cup of water, 2 tablespoons of oil and ¾ teaspoon of salt, covered, over high heat. After about 10 minutes the water is gone and the onions are sizzling.

Then the lid comes off and the onions brown over medium-high for 15 to 20 minutes, pressed against the pan and stirred. A final ⅛ teaspoon of baking soda, dissolved in a tablespoon of water, goes in for the last minute.

Because the baking soda only shows up at the end, the onions finish softened, well browned, and slightly sticky instead of jammy. For onions you can see on top of a pizza, this is the cheat I’d pick. The full batch makes about 2 cups, enough for four pizzas.

How to Put Caramelized Onions on a Pizza

How much: about ½ cup per 12- to 14-inch pizza, the figure from the one surveyed recipe written for pizza specifically. A Pizza Today recipe from Aldo Musico of Aldo’s Pizza in Naples, Florida is in the same neighborhood at 4 ounces per pie.

How far a batch goes: 1½ pounds of raw onions cooks down to about 1 cup, so one batch covers two pizzas. Cook’s Illustrated gets about 2 cups from 3 pounds, the same ratio.

When they go on: before the bake. This is the opposite of balsamic glaze for pizza, which only ever goes on after. In two Pizza Today recipes, caramelized onions bake right on the pie, one at 500°F and one at 550°F for 8 to 10 minutes. They are already cooked, so the oven only has to warm them through at your usual pizza temperature.

Two cautions, both my own reasoning and not test results. Let the onions cool before they touch raw dough, and lift them out of any liquid left in the pan. In an oven running far hotter than a kitchen range, like the ones behind these 900-degree Ooni recipes, tuck them under the cheese so the sugars are shielded.

Pizzas That Want Them

• Blue cheese and walnuts. The classic. Our gourmet pizza ideas include a gorgonzola and walnut pie that uses the onions as the sauce. Gruyere and goat cheese work too; see the best cheeses for homemade pizza.
• White pizza. No tomato means the sweetness has room. Spread the jammy version under the cheese on a pizza bianca.
• Fig and prosciutto. Add a small handful to this fig and prosciutto pizza.
• Cheesesteak. Onions are half the sandwich. Swap these into Philly cheesesteak pizza.
• Flammkuchen. The Alsatian flatbread is built on onions already. Start from our flammkuchen recipe.

A thread of homemade hot honey finishes most of these nicely. For more pairings, see our full guide to pizza toppings.

Caramelized Onions for Pizza: The Recipe

Three Things That Save a Batch

Storing and Freezing

Caramelized onions are a make-ahead ingredient, which is how a 45-minute topping fits a weeknight.

USDA’s guidance on leftovers is the rule I follow. Refrigerate within 2 hours of cooking, use within 3 to 4 days, or freeze for 3 to 4 months. Cool them in a shallow container so the heat leaves quickly.

Some recipe sites say a week in the fridge. I’d rather be boring than sorry. Freeze them in ½-cup portions and each one is exactly one pizza.

Questions People Actually Ask