How to/ Basics,  Recipes,  Sauces

How To Make Easy Caramelized Onions

Caramelized Onions in the Slow Cooker When Done
Completed Caramelized Onions in the Slow Cooker

Question: What’s the easiest way to make caramelized onions?

Answer: In a slow cooker. Just “set it and forget it” as they say.

Believe it or not, onions are naturally sweet and the longer you cook them, the more the natural sugars come out. Eventually, those sugars will caramelize and the onions will become sweeter, almost like a jam. I’ve seen caramelized onion recipes that call for sugar, or add balsamic vinegar, but really, you don’t need anything but the onions, some oil or butter to cook them in, plus some salt and pepper. If you need to add sugar, “yer doin’ it wrong!” (This last bit must be said with a heavy Scottish accent.)

Of course, you can caramelize onions in a pan over very low heat, in less time than in a slow cooker, but this takes attention to make sure the onions don’t cook too fast or burn in the process. If you cook them on too high heat, they may burn before they get sweet. You need to watch them at all times. In a slow cooker, you can take a peek every every few hours, or even ignore it overnight, and get the same, if not better, results.

Caramelized Onions cut and in the Slow Cooker
Caramelized Onions cut and in the Slow Cooker

In the photo above, clockwise from the top left; cut onions, cut onions with oil, salt, and pepper added to the slow cooker, after cooking for four hours, and after cooking for 12 hours in the slow cooker.

Caramelized onions are great on sandwiches (think patty melts, cheesesteaks, roasted pork, grilled chicken), in pasta, in baked dishes like a quiche, casserole, or savory tarts. The list goes on and on. I hope to have some new recipes where you can utilize these deeply flavorful onions coming soon!

The challenge in cooking with caramelized onions as an ingredient is that making them every time you want a little bit is a pain when you just want to complete the dish. You’ll need to cook the onions for an hour or more on very low heat to get the results you want.

Make a big batch and save time later:

No matter how you choose to make them, in a slow cooker or skillet, I highly recommend you make a large batch and portion them out in smaller amounts for later use. You can put them in anything from ice cube trays to small Tupperware or you can try something like the silicon Souper Cube tray below.

I received both the half cup and full cup sizes of Souper Cubes as Christmas gifts (does my family know me or what?) and they are a fantastic way to freeze sauces, stocks, soups, and yes, caramelized onions. The half-cup Souper Cubes were perfect for this recipe. Once they were frozen, I popped them out of the container, wrapped each frozen cube in plastic wrap, and put them in a freezer bag. I’ve already used one block for an eggplant recipe from Ottolenghi’s cookbook Simple that called for caramelizing an onion. What a time saver!

Caramelized Onions in Souper Cubes for Freezing
Caramelized Onions in Souper Cubes for Freezing
Caramelized Onions packaged for the freezer
Caramelized Onions packaged for the freezer (yes, mis-spelled!)

Recipe for Easy Caramelized Onions:

How to Caramelize Onions in a Slow Cooker

The easiest way to make caramelized onions, in a slow cooker
Prep Time10 mins
Cook Time12 hrs
Total Time12 hrs 10 mins
Course: Condiment, Sauce
Cuisine: American
Keyword: caramelized onions, onions
Servings: 3 cups

Equipment

  • Slow Cooker

Ingredients

  • 3 pounds yellow onions sliced thin, about 4 each
  • 2 tablespoons extra virgin olive oil
  • 2 teaspoons kosher salt
  • ½ teaspoon black pepper freshly ground

Instructions

  • Peel the onions and cut them in half. Thinly slice them crosswise.
  • Place the sliced onions in a bowl and toss them with the olive oil, salt, and pepper.
  • Place the onions in the slow cooker, turned on low. Cook for 4-5 hours and then check and give them a stir. You can also put them in when you go to bed and let them cook overnight. They will take 10-12 hours to get to the caramelized (sweet and brown) stage.
    Caramelized Onions in Slow Cooker After 4 hours
  • If after 10-12 hours, they have too much liquid in the bottom of the pot, let them cook for 30 minutes to an hour with the lid ajar so that some of the moisture evaporates.
    Caramelized Onions in the Slow Cooker When Done
  • When the onions are done, cool and refrigerate or freeze. See notes on freezing below.
    Caramelized Onions in Souper Cubes for Freezing

Notes

Caramelized onions should keep for up to 14 days in the refrigerator or up to 6 months in the freezer.
I highly recommend Souper Cubes for freezing sauces, soups, and yes, even caramelized onions. I froze them and then popped them out, wrapped them in plastic, and packaged them up for later use.
Caramelized Onions packaged for the freezer
Caramelized Onions packaged for the freezer (yes, I know they are spelled wrong!)

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Pin this recipe for Easy Caramelized Onions for later!

Easy Caramelized Onions Recipe
Pin This! Easy Caramelized Onions Recipe

10 Comments

  • Susan Claire

    I have always shied away from making these-I was convinced that I would be standing over a hot stove all day or I would burn the heck out of them. Now I can load up my crock pot and walk away! Genius!

  • Pam Valente

    Bless you! Sometimes you realize that the simplest ideas have escaped you. Not long ago I learned that you can freeze whole lemons and limes. That is amazing and why didn’t I ever slow down enough to figure it out?? Caramelized onions made in the slow cooker and frozen for later use?! Brilliant. Thank you and keep blogging the simple and the sublime. That’s what I like about you.

    • formerchef

      Aw, thank you! It’s not something I did all that frequently myself, but I recently bought a 10 lb sack of organic onions and I didn’t want them to go to waste! Freezing whole lemons and limes?? I’m going to have to give that a try! I often freeze the juice, but not the whole fruit!

  • Kate

    Mine are cooking right now and are near the end. I came back to this site to see how dark you took them…yes, I’ll cook a little longer. But oh my! They are already delicious! Mine are still quite wet; I may open the lid a bit at the end. I can’t tell from your photos how much liquid remained.
    I’m happy to trust my judgment on that, but still hope you’ll comment on the liquid at some point.

    Also discovered that my slow cooker cooks hot! At the 4 hour check, I turned it down to warm as the onions were boiling. And at bedtime I just turned it off. Back on this am. All is well.
    Can’t wait to taste the final result. Will be freezing in a muffin pan.

    Love your recipes and stories!

    • formerchef

      Hi Kate-

      Great questions! Yes, I chose to keep them on the lighter side because I thought that might offer a bit more flexibility for later use. When I used the first frozen block, I added it to the pan with some other ingredients and cooked it for about 5 minutes to get a bit more color.
      As for the liquid, there was probably more than what you’d have cooking on the stovetop and no, you don’t want it too “soupy”. On the other hand, I thought because I was freezing them, a little extra liquid couldn’t hurt and would cook off later.
      I think it all depends on how you plan to use the onions. If you want to take them out of the freezer and use them directly, then darker and less liquid is better. If they will be added to something and cooked, then lighter and more liquid makes sense. Honestly though, I don’t think you can go wrong either way. They are very forgiving.

  • Kate

    Thanks! and that’s great that they are forgiving. I often need that in the kitchen! LOL! I’m going to let them cook until they are about the color of yours in the last photo. I say, these are so good that all I really need is a spoon!

  • Kate

    The onions turned out Great! My slow cooker runs hot as I discovered, so I turned them off about 11:00 pm and finished them in the morning. I used a muffin pan to portion them into slightly over 1/3 c.
    I must confess, though, that I added 2T of cognac to them. I always have, so I did. I can’t believe how easy it was. Thanks.

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