My Secret to Cleaning My Cast Iron Skillet? Caramelize Onions!

Ever since a very misguided binge-cleaning session led me to get rid of my nonstick skillet, I’ve been especially dedicated to my cast iron skillet. It’s been more important than ever that I keep it in tip-top shape — nice and clean with a perfectly slick seasoning.

Things were going well … until I decided to bake a couple of sweet potatoes in the oven. I had peeled them, rubbed them with a little oil, and put ‘em in at 400˚ to cook. I figured that I’d use them throughout the week in salads and soups, because even though I don’t love meal planning, I do appreciate having a few cooked veggies on hand. Unfortunately I did not set a timer. Whoops. My nose noticed about 90 minutes later. Something scorched-smelling was coming from my kitchen, and I suddenly remembered my potatoes. I pulled them out of the oven and discovered that they had been way overcooked and my pan was definitely worse for the wear. It was patterned with crusted-on potato parts, and would need a little (a lot of?) TLC to get back to fighting shape.

While I’m a big fan of the  “salt and scrub brush” method, I thought of something a friend had told me recently: Whenever his cast-iron pans are in need of a good clean, he caramelizes onions. 

Wait, what?

You may be skeptical, and I was, too. How could all that caked-on sweet potato gunk be fixed with an innocent onion or two? He admitted that he discovered the secret by accident: His pan was already crusted with browned bits when he started caramelizing a batch of onions. He figured that all of the crusty goodness would make the onions even better. Not only did that happen, he said, but his pans were transformed back to their lustrous selves. I decided to give it a try.

Although caramelized onions are delicious, they’re not something I am in the habit of making. To be sure I was doing it properly, I used Kitchn’s guide to caramelizing onions, and spent a full 50 minutes cooking two gigantic sweet yellow onions. I was mindful to moderate the heat of my gas cooktop; I wanted to take things majorly low and slow, so I didn’t end up with crusty sweet potato bits AND burnt onions.

As the onions finished cooking, my kitchen smelled ah-mazing and I realized that I’d soon have a delicious topper for the bakery bread I’d just purchased. I also noticed that my cast-iron pan was almost back to its shiny, glossy self. All it took was a quick swipe with an oiled cloth (I keep one in a small bowl next to my stove for cast-iron maintenance), and my pan was ready for another cooking session. My pan was so glossy, I could see the reflection of my kitchen windows in it.

The process of caramelizing onions is so good because the alliums slowly pick up the fond (aka “browned bits”) from the surface of the pan. If you’ve ever deglazed a soup pot after sautéing aromatics, you understand this process; it’s the same concept.

1. This does take a while to do. If you’re rocking other cooking projects, or will be home for a bit (and these days, in the wake of a global pandemic, who isn’t?), it is worth the investment of time. But if you’re just looking to clean your pan and move on with your life, try another method.
2. Do not try this if you’ve burnt the bottom of your pan. Run-of-the-mill browned bits will be a delicious addition to your onions. But if the pan looks like it has been to the seventh circle of hell and back, do not waste your time on this method, and instead get to scrubbing (and don’t forget to rub the pan down with oil after washing and drying).
3. Don’t let the pan sit, dirty, in your oven or stovetop for days before cleaning. I am speaking to myself here. Not only would you be short a pan for the length of time you procrastinate, you’d also be seasoning your onions with three-day old food residue. Not ideal.

Have you tried this? Would you? Are we totally out of control? Let us know in the comments!