How to Caramelize Onions

Some ingredients are transformed by cooking. Take vegetables such as fennel, or fruits that you would normally eat raw, but that taste amazing when grilled. 

And so it is with onions. Raw they are sharp. I’m not a fan, although I know folks who do eat slices of raw onion on sandwiches. Lightly sautéed they lose that sharp taste. But honestly, at that point they are just tangy – nice but nothing more. Caramelized, however, is a whole new ball game. While retaining a hint of that tangy flavor, caramelized onions become almost buttery in texture. Their taste is definitely more complex and they have an aroma that is nothing short of heavenly.

Want to know how to caramelize onions? It’s simple. The ingredients are just onions, fat, salt and pepper. Plus liquid at the end – water, vinegar, or wine.

The really crucial element is time. If you have an hour, then caramelized onions are in your future. The long and slow cooking transforms the onions the way long slow cooking takes ribs or brisket from just meat to barbecue. 

Caramelization is a process, not a magic trick. Don’t try to rush it. And while you can find blogposts that claim to provide shortcuts, beware. There is no substitute for this process, though you may be able to achieve it in different ways. (I’ve never tried the slow cooker method and I suppose an Instant Pot would work.) In any event, the rewards are worth the time you put in.

Besides, caramelized onions last in the refrigerator for as long as a week. Make them in an hour when you have some downtime and reheat them in a microwave or on the stove for use in lots of dishes. You can freeze caramelized onions too. So if you’re taking the time to tend the onions, might as well make a double batch. While onions do cook down considerably as caramelize, a little goes a long way. 

Step-by-Step Instructions on How to Caramelize Onions (with Tips)

1. Preparing the onions – Slice the onions. (Chopping them works, but the result is not as pretty.) I like to use a food processor. or slice them by hand. You can also use a mandoline. (I used one for the potatoes and onion slices in my No Fuss Potato Casserole.) However, I find the mandoline more trouble than it is worth for this purpose. A food processor with a 4 mm slicing disc does just fine. And if you’re fast at hand slicing, do that. These slices do not need to be paper-thin. 
2. Use about 1 tablespoon of fat per eight ounces of onion. Figure that each medium-large onion is about eight ounces. I like to use half butter and half olive oil. For butter or other non-liquid fat, melt it first. (I put both the butter and oil in the pan so they mix together while the butter melts.) Then toss the sliced onion with the fat. Use a heavy pan, preferably one that is cast iron. I use a 10-inch pan (measured at the top) for one pound of onions and a  12-inch pan for two pounds. 
3. Once the onions are coated in the fat, cook them over a medium-low flame. Depending on the heat and other factors, it will take 45-60 minutes for the slices to turn from white to golden to brown. Be sure to stir every few minutes. If you are inclined to, set a timer, and do something else nearby. Stirring avoids burning and ensures that all pieces get a chance to touch the bottom of the pan. The onions go from from stiff and sharp to smooth and  melt-in-your-mouth delicious.
4. After the onions are done, take them out of the pan and add a small amount of liquid to the pan to scrape up what is left. Drizzle the liquid over the onions and use them immediately or refrigerate/freeze them for later. 

Here’s how the onions progress from raw to done in 45-60 minutes.

Onions when they first go in the pan, coated with the fat and ready for their long, slow cooking:

My dream is to fry up a bunch of bacon, use the fat for the caramelized onions and crumble the bacon back into the onions. Then schmear the stuff on rye bread and bite into it – savory heaven!

After 15 minutes, the onions are less stir and they become begin to lose their bright white hue:

With another 15 minutes (after cooking for 30 minutes), they are starting to brown:

After 45 minutes, they turn golden (Sometimes they caramelize completely in 45 minutes. But not in this instance.):

And finally, after 60 minutes, they are golden brown:

How can you use caramelized onions? Here are just a few ideas:

• In my Apple and Caramelized Onion Chutney  
• On a tomato and mayonnaise sandwich (in the spring/summer when you can get decent tomatoes) 
• Or on white pizza. 

5 from 1 vote

Print

Caramelized Onions

An easy way to caramelize onions and take them to a whole new level.

Cuisine American

Keyword caramelized onions, onions

Prep Time 10 minutes

Cook Time 45 minutes

Total Time 55 minutes

Author Laura

Ingredients

• 1 pound onions Thinly sliced works best, but chopped is OK too. One-pound equals about 2-3 medium-large onions.
• 2 tablespoons fat (oil Butter, olive oil, or a combination - or other fat such as bacon drippings)
• 2 tablespoons water Alternatively, use wine, juice or vinegar (I like light vinegar such as apple cider or unseasoned rice wine vinegar but balsamic works too)

Instructions

1. Toss the onions in the fat (melted, if the fat is solid at room temperature.)

2. Cook the onions in a heavy pan over a low heat for 45-60 minutes, stirring every 5-10 minutes.

3. Remove the onions when done, then add the liquid to the pan. Scrape up the browned bits and liquid and add them into the cooked onions. Use salt and pepper to taste.

Recipe Notes

Cast iron pans are an excellent choice for caramelizing onions because they retain the heat while minimizing burning. Heavy gauge stainless steel also works fine. Avoid light pans, which may not prevent burning and those with no-stick coating, which inhibit browning and caramelization.

Onions sizes can be tricky. I prefer to weigh my onions. One-pound of onions, sliced and cooked down ends up to be about 3/4 cup of caramelized onions. 

What’s your favorite way to use caramelized onions?