Caramelized Onion, Spinach, and Avocado Quesadillas

By Julia Mueller | Last Updated: May 24, 2015

Caramelized Onion, Spinach & Avocado Quesadilla

Caramelized Onion, Spinach, and Avocado Quesadillas
An avocado a day keeps the doctor away. Okay, that statement may need some fact-checking, but I do eat a whole avocado most days — so I’ve made it my motto as well as my M.O. Adding avocado to a hot, melty quesadilla may seem strange, but let me assure you: it just works. For these Caramelized Onion, Spinach, and Avocado Quesadillas, you simply add the sliced avocado at the very end of the cooking process so it doesn’t get overly hot or mushy.

Caramelized Onion, Spinach, and Avocado Quesadilla
Caramelized onions definitely take their fair share of time to cook, but they’re so worth it. They add rich, deep flavor to a meal, which makes you feel fancy — even though you secretly know they’re a cinch to make. The onions cook down quite a bit, so I use two for this recipe. To caramelize them, start by adding 3 to 4 tablespoons of oil to a skillet, add the onions, and sauté over medium heat. The onions will sweat, then turn translucent, and then finally brown into caramelized goodness. The best thing about caramelized onions is that they freeze well! So you can make a big batch when you have time, keep ’em in the freezer, and use them whenever you need an emergency quesadilla.

Those sweet caramelized onions paired with creamy avocado make a delicious quesadilla on their own, but we also invite spinach, because: vitamins. Since everything on the inside of this quesadilla is soft, I like to make the tortilla crispy to add contrast. I cook the quesadilla on medium-low heat for a few minutes so that the tortilla crisps up nicely, but doesn’t burn. Who would have thought all you need for a fancy, flavorful quesadilla is onion, spinach, and avocado?

Enjoy this crispy/creamy quesadilla with your favorite salsa or cilantro pesto.

This post was originally published on May 12, 2014.

Go to Caramelized Onion, Spinach, and Avocado Quesadillas recipe

Caramelized Onion, Spinach, and Avocado Quesadillas

Prep Time:

5 minutes

Cook Time:

1 hour

Total Time:

1 hour, 5 minutes


4 quesadillas


  • 3 tablespoons grapeseed oil or olive oil
  • 2 large yellow onions, halved and sliced
  • 1/2 teaspoon salt
  • 10 ounces baby spinach
  • 2 cups shredded Monterey jack cheese
  • 2 avocados, pitted, peeled, and sliced
  • 4 large flour tortillas
Print recipe


  1. Add the oil to a large sauté pan over medium heat. Add the onions and salt and cook, stirring occasionally, until the onions are soft and deep golden brown, about 30 to 40 minutes. (If the sides of the onions begin cooking too fast, lower the heat to medium-low, add a little more oil, and stir. Your goal is to have the onion slices cook as uniformly as possible.) Remove the onions from the pan and place them in a bowl.
  2. In the same sauté pan over low heat, add the spinach and cook, stirring frequently, until wilted, about 2 minutes. Remove from heat and transfer the spinach to another bowl, then carefully wipe the pan dry with a paper towel.
  3. Return the pan to the stove and increase the heat to medium-low. Lay one tortilla flat in the pan. Evenly sprinkle 1/2 cup of cheese over the top. To the bottom half of the tortilla, add 1/4 of the caramelized onions, followed by 1/4 of the wilted spinach. Heat until the cheese melts and the tortilla is browned and crispy.
  4. Add the avocado slices (about 1/2 of an avocado per quesadilla), and immediately fold the tortilla in half, onto itself, and flip it over. Continue cooking for about 30 seconds or until warmed through.
  5. Using a spatula, transfer the quesadilla to a cutting board. Cut into fourths. Repeat this process with the remaining ingredients and serve with your favorite salsa or cilantro pesto.

About Julia Mueller

Julia Mueller writes the food blog, The Roasted Root, and is the author of Delicious Probiotic Drinks and Let Them Eat Kale!. A Lake Tahoe native, Julia loves to play outdoors, and enjoys developing recipes that are nutrient-dense and approachable to make any night of the week.

Read more from Julia Mueller

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I did not know that caramelised onions froze so well. Good tip, thank you!

These quesadillas look delicious and I am planning to make them for a lunch. Do you think pita bread would work as I’m not sure where might sell tortillas around here?

I saw this recipe today and knew this was what was for dinner. Absolutely delicious and so easy – this had my husband asking for these to be put into the meal rotation. Thank you!

Just got done eating these! I had all the ingredients so whipped it up! SO YUMMY!!!! Did not know I could freeze caramelized onions, good to know!

I always love your recipes! So many, like this one, end up as a Recipe of the Day on my Facebook page. Looking forward to trying this one. Now I’m off to learn about that cilantro pesto, something I hadn’t heard of until now.

I love this recipe and would love to pin the specific recipe page (not the whole website). Is there a way to just pin this recipe to my pinterest account? Thank you!

Hi Irina, Make sure you are on the actual recipe page (not just the homepage), hover over an image and click in the “pin.” That should allow you to pin it. Otherwise, if you click on the red Pinterest widget at the bottom (under the author bio), that should allow you to pin the recipe!

This has become an every other week staple in my kitchen and is delicious! Wonderful combination of flavors and textures make this one a go to for company or just a night at home with the boyfriend. Fast to cook, faster to eat, and an easy clean up at the end. Perfect!

I had no idea you could freeze caramelized onions; thanks for the tip. Also thanks for acknowledging how long they take to make. I cannot believe the number of recipes I read that say it takes about 15 minutes to caramelize onions and it simply isn’t true.

Caramelizing onions the right way takes a lot of time–they should be cooked low & slow. Some recipes will cook them on medium heat for 15 minutes or so, but that’s not truly caramelized.

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