The whole point of freezing things is to have ingredients on hand right when need them. If you haven't heard it before, caramelized onions freeze wonderfully well and are great flavor boosters for almost any food. Read on for freezing tips and quick fix uses!
Caramelizing onions sounds like more of a process than it really is. Onions practically do it on their own if left alone in a pan. We've covered the key steps here, and can't emphasize enough to make more than you'll need. A medium onion cooks down to about a cup once caramelized, so why not cook a few while you're at it? And don't stop at regular onions — caramelizing works great with red onions and shallots, too!
Adding stock or wine to the pan of onions kicks up the flavor even more and keeps all those browned bits stuck to the pan from going to waste. I like cooking my onions in a heavy bottomed stainless steel pan because the onions brown better than when using a nonstick pan.
I find that caramelized onions freeze best in ice cube trays. Pile them in, let them freeze until solid, and transfer to a heavy duty plastic bag or other freezing container.
Pasta Sauces: Tomato pasta sauce just begs for some caramelized onion flavor, especially the store bought variety. These onions are a great start for roasted vegetable pasta as well.
• Marcella Hazan's Famous Tomato Sauce
• Farfalle with Chicken, Tomatoes, Caramelized Onions, and Goat Cheese from Bon Appetit
Pizzas and Flat Breads: Caramelized onions trump raw onions any day, and they pair well with a spicy tomato sauce or creamy goat cheese.
• BBQ Chicken Pizza With Caramelized Onions
• Flatbreads with Goat Cheese, Caramelized Onions, and Basil
Sandwiches: It's no secret that onions make a burger and transform a sandwich. Let a cube or two of frozen caramelized onions thaw in the refrigerator or nuke them for a few seconds and add to anything that needs a little something extra.
• Chicken Breast Sandwiches with Caramelized Onions, Watercress and Paprika Aioli from Bon Appetit
• Old Fashioned Juicy Burgers
Vinaigrettes: Whisk caramelized onions in with these vinaigrettes to add smokey flavor, or top salads with onions to complete the dish.
• Green Beans with Caramelized Onion Vinaigrette from Real Simple
Side Dishes: It's a big category, but many side dishes from roasted vegetables to rice will benefit from adding caramelized onions. Either use them to start off the cooking and infuse flavor into the whole dish, or warm and add as a delicious garnish.
• Couscous with Caramelized Onions & Tomatoes
• Baked Mushroom Risotto with Caramelized Onions
Related: Fast Flavor: The Quickest Way to Caramelize an Onion
(Images: Stephanie Barlow)

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The Sandwich links are broken. :(
I started doing this after reading a previous Kitchn post and it has totally been life-changing. When I make a big batch I like to freeze them flat in a big Ziplock, so I end up with a "sheet" of onions and it's easy to break (or slice) off as much as I need.
I've never thought to do this. Thanks for the idea!
I like the Ziploc tip, too. It works great for sauces, too, like pesto.
Am I doing something differently? I find that if I use, say, a medium sized onion, I get far less than 1 cup, caramelized.
I caramelize my onions overnight in a crockpot so there are a LOT of them and freezing them is the perfect antidote to having so many. We end up with them in a lot of things that I would never take the time to do each time I cook. Scrambled eggs are a favorite.
Hi, I love the recipes you share. Could you add the photo to the Print option if possible, please? Thanks so much!