The short answer: to caramelize onions, slice 2 large yellow onions thin, cook them in 2 tablespoons of butter or oil in a wide pan over medium-low heat for 30 to 45 minutes, stirring every few minutes, until deep golden brown and soft.
- Time: 30 to 45 minutes (Mississippi State University Extension says 30 to 40)
- Yield: 2 large onions make about 1 cup
- Do not: use high heat or crowd the pan
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Caramelized onions turn a cheap bag of onions into the sweet, savory base for soups, burgers and pizza. The only real ingredient is time: the water has to cook out slowly so the sugars brown without burning.
Ingredients
| Ingredient | Amount |
|---|---|
| Large yellow onions | 2 |
| Butter or olive oil | 2 tablespoons |
| Salt | 1/2 teaspoon |
| Water, broth or vinegar | 1 to 3 tablespoons, only if the pan gets dry |
How to caramelize onions
- Peel the onions, cut them in half through the root and slice them thin, about 1/8 inch, so they cook evenly.
- Heat the butter or oil in a wide, heavy skillet over medium-low heat.
- Add the onions and salt and stir to coat. Cook for 10 minutes, stirring every few minutes, until soft and translucent.
- Keep cooking over medium-low for 20 to 35 more minutes, stirring every 3 to 5 minutes and scraping up the brown bits.
- When the pan looks dry or the browned bits stick, stir in a tablespoon of water, broth or vinegar to loosen them.
- Stop when the onions are deep golden to mahogany brown and jammy. Taste and add salt if needed.
Caramelizing stages
| Stage | About how long | What it looks like |
|---|---|---|
| Sweated | 10 minutes | Soft, translucent, no color |
| Golden | 20 to 25 minutes | Light gold, slightly sweet |
| Caramelized | 30 to 45 minutes | Deep brown, jammy, very sweet |
These are typical times for a wide skillet over medium-low heat. A crowded pan or higher heat changes them.
Tips for better caramelized onions
- Use a wide pan: a 12-inch skillet lets moisture escape. A small pan steams the onions.
- Keep the heat medium-low: high heat scorches the edges before the middle softens.
- Salt early: salt draws water out of the onions so they soften sooner.
- Deglaze: a splash of water, broth, balsamic or wine lifts the brown bits and adds flavor.
- Make a big batch: they keep 3 to 4 days in the fridge, so cook extra for the week.
How many onions to start with
Onions cook down by a large fraction. As a working rule from this method: 2 large onions make about 1 cup, so scale the pan size and time up when you cook 4 or more.
What to make with caramelized onions
Use them in French onion soup, on a baked potato, stirred into soup recipes or stacked on a burger. A pot of beef stew also gets sweeter with a spoonful. A bag of onions is one of the cheapest items on the list: compare prices with a grocery price book and see meal planning on a budget.
Storing caramelized onions
Cool the onions within 2 hours and refrigerate them in a covered container for 3 to 4 days, per USDA leftover guidance. For longer storage, freeze them in tablespoon portions on a tray, then bag them.
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Frequently asked questions
How long does it take to caramelize onions? Caramelizing onions takes about 30 to 45 minutes over medium-low heat. Mississippi State University Extension says it takes about 30 to 40 minutes while the water cooks out of the onions and the sugars turn golden brown. Faster methods exist, but they brown rather than fully caramelize.
What kind of onions are best for caramelizing? Yellow onions are the usual choice because they are sweet enough and hold up to long cooking, with white and sweet onions also working. Red onions give a jammier, slightly tangier result. Slice them thin and evenly so they cook at the same rate.
Why aren't my onions caramelizing? Onions that stay pale usually need more time or a pan that is not crowded. Use a wide pan, give them at least 30 minutes, stir every few minutes, and add a splash of water when the pan looks dry. If they scorch before softening, the heat is too high.
How many onions do I need? A large yellow onion makes about 1/2 cup of caramelized onions, because they cook down to a fraction of their raw volume. For about 1 cup finished, start with 2 large onions, and use a wide pan so they cook in a thin layer.
Do you need sugar to caramelize onions? No. Onions contain natural sugars that brown as the water cooks out, so no added sugar is needed. A pinch of sugar or a splash of water, broth or vinegar can help a pan that is browning too slowly or sticking, but it is optional.
How long do caramelized onions keep? Caramelized onions keep about 3 to 4 days in a covered container in the refrigerator, based on USDA leftover guidance, and can be frozen in small portions. Cool them within 2 hours of cooking before storing.
What can you do with caramelized onions? Caramelized onions go on burgers, pizza, grilled cheese, baked potatoes and flatbreads, and into soups, dips and omelets. The classic use is French onion soup, which depends on a deep golden-brown pot of them.
Can you caramelize onions in a slow cooker or oven? Yes, both work with less stirring but still take hours: a slow cooker uses low heat for many hours and an oven uses a covered pan. The stovetop method here is faster and gives you control over browning, so it is the best place to start.
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Sources
- Mississippi State University Extension: How to Caramelize Onions extension.msstate.edu