How to Make Caramelized Onions in the Microwave

How to Make Caramelized Onions in the Microwave

Thoroughly caramelizing onions, that is removing most of their moisture and converting the natural sugar to mahogany-dark, candy-like goodness, (not to mention the conversion of amino acids to brown deliciousness via the Maillard reactions), can be achieved on the cook-top or even in the oven. But doing so requires vigilance, careful heat control and a heck of a lot of stirring.

This method requires a glass bowl and a microwave oven. So …


  • 4 large yellow onions (enough for 2 pounds, sliced thin)
  • 1 tablespoon dark brown sugar*
  • 1 tablespoon butter
  • 1 teaspoon kosher salt
  • 1/4 teaspoon baking soda**
  1. Peel onions and slice thin (3mm) on a mandolin, or quarter and run through slicing blade of a food processor. (I personally prefer the ceramic blade, hand-held mandolin by Kyocera and no, they don’t pay me to say that.)
  2. Place half the onions in a large glass mixing bowl and toss with half the salt. Add the rest of the onions and sprinkle with the remaining salt. (Although salt will certainly enhance the flavor of the final result, it’s being added here for it’s ability to pull moisture out of the onions.)
  3. Cover tightly with plastic wrap and microwave for 10 minutes.
  4. Uncover (carefully … steam hurts) and drain to pour off any excess moisture. Stir in the butter, baking soda and brown sugar.
  5. Microwave uncovered for 15 minutes.
  6. Stir thoroughly then drain excess liquid again.
  7. Microwave 15-20 minutes more at 3 minute intervals, stirring thoroughly after each until the desired level of brownness is achieved.

NOTE: All use of microwave is at high-power only.
* Although the onion will probably be sweet enough on their own, I like the complexity of the flavor that the molasses in the brown sugar adds.
** Adding even a small amount of baking soda increases the pH of the onions, which promotes browning. It’s the same reason pretzels are dipped in a lye solution before baking.

So now that you have caramelized onions …

1. Add them to a frittata

2. Top crostini with onions and goat cheese or something stronger like gorgonzola

3. Take finished onions and shredded Gruyere and toast until melted (photo below)

Caramelized Onions and Gruyere Toast

Recipe and images © Alton Brown, 2015.


Add yours
  1. 1
    ALex Ortiz

    I personally LOVE reading all the comments, critiques and suggestions. It can be very instructive and inspiring sometimes. And, as Viola on July 22, 2015 stated, there are situations when a microwave might be the best answer. Thanks.

  2. 2
    Jenn C

    Made a small batch tonight (only had 2 smallish onions) and it definitely affected cook time. I expected this so stayed in the kitchen. Initial cook was approx 7 minutes, second cook after adding brown sugar, etc was approx 4 minutes. Onions were delicious. I love this technique and will be using it ALL summer!!!

  3. 3
    Sarah F.

    Tried it this morning and it caught fire about 7 minutes in on the first microwave. Onions blackened to a crisp and the plastic wrap caught on fire. Either my wattage was too high, 1100, or it’s not ok to cook fewer onions at a time. My microwave is ruined – I blame myself I should have watched it the first time.

    • 4

      Me too!!! I needed to add a few extra onions to a french onion soup in a crockpot that had already been simering a few hours. I decided to soften some up quick using this method. They caught on fire with clouds of smoke billowing out of the microwave. Probably completely destroyed my appliance.

  4. 5
    Jose Albaine

    I love how food can be micromanaged to the point of absolute control. I caramelize my onions on the stove, with baking soda as well, no salt and a bit of butter. They will break down pretty fast, but here’s the trick to prevent burning before they are ready: when the moisture is about to dry out (no water means carbonization happens), add a sprinkle of water, and keep stirring. Water buys you time, and time and movement is all you need to get to that delicious dark brown flavor. When you get to the color intensity that you want, that last splash of water, dissolve some salt in it before adding it (flavor, and i find it gets rid of the alkaline taste of baking soda, if you put too much). The butter in the beginning will make it silky, and it will have the consistency of spreadable jam. This thing is food gold, i try to always keep a quart of it in the fridge, and i add it to anything i cook. It pretty much makes perfect instant french onion soup, if you have some nice beef stock or broth, and you add some fine sliced shallots for texture.

  5. 6

    some people are microwave cooks, some are old fashioned cooks, some are both, any method that works for you are the best. it is great we have all these ideas out there to help us. keep up the good work and ideas.

  6. 7
    Ashley B.C.

    Love, love, love it! I’ve spent many an hour caramelizing onions in a pan the #oldschool way, but since it can be done in the microwave with less attention and exercise (haha), I’m game! In all fairness, I’ve done both microwave caramelized onion and slow-cooker caramelized onions. I always find that while the slow cooker is super easy, if you want true caramelized onions, at some point your going to have to get the moisture out by human intervention and not purely by evaporation….Maybe it’s because my slow cooker has a super gasket seal or I’m just impatient. All in all, my go to is the microwave. Thanks AB!


  7. 8

    I just tried this and I got the “staying yellow and getting mushy” that a couple other people have mentioned. That being said, it tastes good, just not quite caramelized. I’m speculating it’s because I didn’t pour off enough liquid after that second microwaving. So I will try it again in the interests of science. 🙂

  8. 9
    Kathy T.

    I personally LOVE reading all the comments, critiques and suggestions. It can be very instructive and inspiring sometimes. And, as Viola on July 22, 2015 stated, there are situations when a microwave might be the best answer. I think that I will try Alton’s recipe but in the crockpot and see what happens!

  9. 11

    Regardless of which method may be “better” it’s good to know that it’s possible in a microwave. What if all your burners are in use? What if the gas lines are being worked on in the neighborhood? What if you live in a studio apartment w/o a full kitchen? There are any number of reasons one might want to use a microwave and I’m glad to know this works.

  10. 13

    Started out well, but burned them black in the second cooking…. should NOT have stepped away! Will try again and watch them closely!

  11. 16

    Just tried this and it worked perfectly. I’ve never managed to do this well on the stove top as even at low (1) they always seemed to burn. Thanks to Mr. Brown I’ll now have caramelized onions whenever I want with no burnt bitterness!

  12. 17

    I was surprised how good these were, so glad it worked. I teach a life-skills class for kids aging out of foster care and am always glad to find micro wave recipes for real food.

  13. 19

    Not a good product. Onions were mushy, yellowish, and lost their substance. After sitting, they were gummy little clumps. I gave up after 8 3-minute intervals. I would call this a failed recipe and a waste of onions.

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