Slow Cooker Caramelized Onions are mellow, sweet, and versatile, too! Use them for everything from French onion soup to omelet fillings to burger toppings. With this simple, foolproof method, you can have caramelized onions on hand anytime!
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Slow Cooker Caramelized Onions are sweet, mellow, and so versatile! Not only can you make some out-of-this-world French Onion Soup with them, but they make a tasty addition to beef dishes, dips, omelets, burgers, and sandwiches – just to name a few.
Why caramelize onions in a slow cooker instead of on the stovetop?
Caramelizing onions the traditional way – on the stovetop, low and slow – can be frustrating and time-consuming. This simple, foolproof slow-cooker method bypasses the skillet and stovetop altogether; and allows you to have caramelized onions on hand anytime, with minimum effort and no fuss.
What kind of onions work best for slow cooker caramelizing?
The type of onions you use can affect both the cooking time and the sweetness level of your finished onions. Personally, I prefer to use a mixture of red and yellow onions.
It may seem counterintuitive, but avoid using sweet onions for caramelizing.
Sweet onions will work, but will take significantly longer to cook, and the end-product has less flavor than that made with red and/or yellow onions. This has to do with the fact that, while we perceive sweet onions to be sweeter, yellow and red onions have more of those pungent lachymators (i.e., stuff that makes you cry) than do sweet onions (e.g., WallaWallas, Vidalias, etc.), giving the impression that they are significantly less sweet.
The truth is that yellow and red onions actually have a far more complex flavor profile, and yield richer, more flavorful caramelized onions.
A mix of red and yellow onions turns a nice brown-burgundy color in the slow cooker; and since both red and yellow onions have a lower moisture content than sweet onions, the cooking process is measurably shorter. The higher sugar content of the red and yellow onions makes for great caramelization, and they never require additional sweetening.
Given the super-long cooking time, I usually start cooking my onions in the evening, and let them cook all night long unattended. Then I can stir them once in the morning, check how far along they are, and gauge the rest of the time needed from there.
You can also start them at the beginning of your workday, and then check them again when you get home.
Post & Recipe updated September 8, 2020 (Originally published November 11, 2013)
Slow Cooker Caramelized Onions
Equipment
Ingredients
- 4 - 5 pounds onions (yellow, red, or sweet)
- 3 tablespoons olive oil
- 1 teaspoon kosher salt
Instructions
- Slice onions from pole to pole (root to stem), about 1/8"-1/4" inch thick.Cutting the onions this way prevents them from breaking down too much during cooking.
- Fill Slow Cooker about 2/3 full of cut onions.
- Drizzle in olive oil and toss to coat.
- Cover slow cooker and set to LOW.
- Cook for 10-18 hours, stirring every few hours if you are available. (It's also OK if you don't stir them at all.) This step is done when the onions are dark brown, soft, and swimming in a thick liquid. Image: Onions after 5 hours
- When onions are medium brown, soft, and sweet, they are ready to use. Image: Onions after 8 hours
- For thicker, jammier caramelized onions with deeper color, uncover the slow cooker and continue to cook onions on low for an additional 3-5 hours. Image: Onions after 22 hours
- Caramelized onions may be used immediately, or refrigerated or frozen for later use.
Notes
Nutrition
Looking for a unique, delicious way to use caramelized onions? Try our Cherry Tomato Tart with Caramelized Onions – It’s pretty fabulous!
I like to use my vacuum sealer to package my caramelized onions for freezing. (Package in one or two cup servings for ease of use.) Vacuum-sealed onions can last up to a year in the freezer.
Ice cube trays are another great option for freezing caramelized onions: small portions are perfect for throwing on a sandwich or burger, topping a pizza, or making an omelet.
Delicious Recipes Using Caramelized Onions
Love caramelized onions? So do I! Here's some great recipes that use them in unique and delicious ways!
Apple, Beet, & Caramelized Onion Pizza
Get ready for one of those “fancy restaurant pizzas” that you can make at home! This Apple, Beet, and Caramelized Onion Pizza has a pink garlicky beet sauce and is topped with cheddar cheese, caramelized onions, crisp apples, and fresh thyme.
Caramelized Onion Bacon Dip with Blue Cheese
A perfect appetizer, this Caramelized Onion Bacon Dip is a revamped version of classic onion dip.
Classic French Onion Soup
Caramelized onions, fresh herbs, flavorful broth, and melty cheese combine to make this classic French onion soup. (Just don't tell anyone how easy it is to make!)
Little Oven Annie's Cherry Tomato Tart
Feta, caramelized onions, and walnut pesto create a savory bed for fresh cherry tomatoes in this beautiful Cherry Tomato Tart.
Caramelized Onions Sautéed Green Beans
A delicious and easy veggie side dish! Sweet caramelized onions sautéed with crunchy green beans, toss with garlic, butter, sea salt, then topped with shaved almonds.
One-Pot French Onion Farro
With tender-cooked farro grains and French onion flavors, this easy one-pan favorite is like a cross between risotto and French onion soup. Serve with Gruyere-topped crostini and a fresh sprig of thyme and we're talking swoon-city.
Caramelized Mushroom, Onion & Cheese Bites
Mushrooms and sweet onions are caramelized with balsamic vinegar, and then baked with cheese on buttery, and flaky puff pastry. These bite-sized appetizers are easy to make and such a crowd pleaser!
Roast Beef Sliders with Caramelized Onions
The best Roast Beef Sliders on the web! They feature tender, caramelized sweet onions, creamy french onion dip, roast beef, and melted cheddar on garlic buttered brioche buns.
Butternut Squash Quiche with Caramelized Onions
This vegetarian butternut squash quiche is filled with caramelized onions and goat cheese, is easy to make ahead of time, and is perfect for brunch!
Vegan Onion Gravy
This gluten-free and vegan gravy is made with caramelized onions and roasted garlic, and is the perfect sauce for mashed potatoes!
French Onion Gouda Stuffed Meatballs
The flavors of French onion soup and smoked Gouda cheese are combined to make the perfect French Onion Gouda Stuffed Meatballs.
Summer Squash Tomato and Onion Galette
A simple recipe that has a soft sweet interior, a zesty creamy cheese filling and just enough of a flaky crust to hold it all together.
Arugula, Brie, and Caramelized Onion Pizza
Upgrade your pizza night by making homemade pizza with caramelized onions, mushrooms, fresh baby arugula and brie cheese! A little bit of sweet along with a little bit of peppery flavors!
Caramelized Onion White Bean Dip
This creamy white bean dip packs a ton of flavor from caramelized onions! It makes a delicious snack or spread.
Vegan Caramelized Onion Dip
Get ready to ditch the pre-made onion dips for good! This easy to make crowd-pleasing dairy-free dip is perfect for parties or Game Day snacking!
French Onion Pasta Bake
With caramelized onions, tender juicy chicken, and melted gruyere cheese over the top, this is an easy/flavorful dinner for the whole family.
Caramelized Onion and Goat Cheese Tart with Thyme
This lovely French-inspired Caramelized Onion and Goat Cheese Tart with Thyme has a flaky, buttery crust, onions cooked until practically melted, tangy goat cheese and fresh thyme.
Brown Butter & Caramelized Onion Mashed Cauliflower
Brown butter and caramelized onion mashed cauliflower is a delicious paleo recipe that will have you forgetting about the potatoes.
Pumpkin Goat Cheese Dip with Caramelized Onions
Pumpkin goat cheese dip with caramelized onions can be served warmed or cold, it’s a great addition to your party spread and perfect for the holidays. Try it with crackers, sliced fall/winter fruits or vegetables!
Pasta with Chicken, Caramelized Onions & Balsamic
Pasta, caramelized onions and balsamic - what’s not to love?!
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