I’m always on the hunt for things that make it easy to add big flavor to dishes on the fly, and slow cooker caramelized onions do just that. Usually when I see a recipe calling for caramelized onions, I roll my eyes — who has 45 minutes to constantly stir just enough onions for the quarter cup you need for your recipe? Not me! That’s why I’m a big fan of making them in a huge batch in my slow cooker. Just slice, leave overnight, and enjoy. Once they’re done, I freeze them in ice cube trays and transfer to a zip-top bag. Whenever a recipe calls for caramelized onions, I just take out a cube or two to use. Though making caramelized onions takes a fair amount of time in your slow cooker, it’s totally hands-off, and this recipe makes enough that you won’t have to worry about running out any time soon. Once they’re ready, use them as a filling for your next batch of pizza donuts or toss them with homemade vegan pasta for an instant boost of long-simmered flavor.

Slow Cooker Caramelized Onions

Recipe from Justina Huddleston, Brit + Co

(Yields about 3 cups of caramelized onions)


  • 6 yellow onions, sliced very thin
  • 2 shallots, sliced very thin
  • 1/2 teaspoon fine sea salt
  • 1/2 teaspoon dried thyme
  • 1/4 teaspoon freshly ground black pepper
  • 1/3 cup marsala wine
  • 1 teaspoon olive oil


1. Peel and slice onions and shallots into very fine slices.

2. Add onions, shallots, salt, thyme, pepper, marsala, and olive oil to your slow cooker. Set to “low” and cook for 8-10 hours, until onions are soft and golden brown.

3. If you want your onions to get even more caramelized, set the slow cooker to high and remove the cover. Let the onions cook until most of the liquid has evaporated and they’ve reached your desired color and consistency. Season to taste.

4. You can use your caramelized onions right away, or freeze them to use later.

They’re great swirled into fluffy mashed potatoes, mixed into cream cheese and smeared on bagels, or added to hot sandwiches — the possibilities are endless.

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(Photos via Justina Huddleston / Brit + Co)