Adult Grilled Cheese With Cinnamon Caramelized Onions

2 Sandwiches
35 min

I don't care what season it is - I ALWAYS love cheese! I'm forever experimenting with new mac n cheese and grilled cheese recipes - so fun! The inspiration for this fun grilled cheese twist came to me as I was making caramelized onions for some savory tarts... I was experimenting with a Cinnamon Toscana Cheese from Trader Joe's and was thinking through how to get that great flavor when the cheese isn't in I began to experiment! I've added these onions to other things as well, like quesadillas and breakfast burritos....and the great news is you can make them ahead of time and store them in the fridge! Then you can easily add some savory flavor to your dishes! Enjoy.

Caramelized onions with savory cinnamon combine beautifully with gooey Fontina to make a sophisticated version of a childhood favorite!


  • 4 slices of good bread
  • Fontina cheese, 2 – 4 ounces
  • American cheese (buy a block from the deli; see notes), 2 – 4 ounces

Cinnamon Caramelized Onions

  • ½ Large or 1 medium onion
  • 1 Tbsp unsalted butter
  • Kosher salt
  • ½ tsp cinnamon

Tools & Timing

  • Prep bowl
  • Sharp knife
  • Cutting board
  • One medium saucepan (lid recommended)
  • One medium pot
  • Wooden spoon
  • Measuring spoons
  • Tongs (recommended)
  • Spatula
  • Timing: 35 minutes; yields 2 grilled cheese sandwiches


I learned to caramelize onions from Bon Appetit…and then added my own spin by adding the cinnamon for a sweetly savory experience


Caramelize the onions: begin after puff has been thawing for 10 minutes

There are many different articles out about caramelizing onions. I read the article “Caramelized Onions” on Bon Appetit, decided to chop my onions my own way, chose the “French onion soup” option, reduced the number of onions to be cooked (and the recipe accordingly), and added a twist.

  1. Prep onion (Hold hairy root and cut off the opposite end. Peel onion so you retain the hairy root – you’ll use this to grip the onion as you slice it. Carefully cut the onion in half almost to the root. Holding the root, slice into wedges that are ¼ inch– separate into a bowl so all pieces come apart – push arcs apart if necessary).
  2. Heat 1 Tbsp unsalted butter in large pot over medium-high heat (I find a dark-coated pot works best).
  3. Once butter starts to sizzle, begin to add onion, a handful at a time. Stir constantly with a wooden spoon. Cook 2 minutes, then add another handful. Repeat process until all onions are in the pot (I did this 3 times to cook one onion). Make sure to cook your last handful for 2 minutes before proceeding to the next step…
  4. Add in a pinch of kosher salt and stir.
  5. Reduce heat to medium-low and cook for 20 minutes, stirring every few minutes to prevent onions from burning.
  6. When the onions begin to turn gold and translucent (this took me a total of 20 minutes), remove pot from heat and stir in cinnamon.

Make your Grilled Cheese

*Prep your bread and slice your cheese when you have 3-4 minutes left on your timer for the onions.

  1. Slice your bread (I like mine a little thicker, but when making grilled cheese, I’d suggest your follow your heart).
  2. Butter one side of each piece of bread; make sure your spread the butter uniformly across one entire side of piece.
  3. Slice your cheese (the amount of cheese needed will depend on the size of your bread – cut enough to create a single layer across each slice – and make sure to cut your slices pretty thin and even so the cheese melts uniformly).
  4. Place bread, butter side down, into your frying pan. Layer American cheese on one piece and Fontina on the other. Using your tongs, place a layer of your cinnamon caramelized onions on top of your Fontina cheese. Turn the heat to medium-low and cover with your lid.
  5. Cook until the bottoms of your bread are golden brown (checking so you don’t burn) – this took me about 7 minutes. Once both sides of bread start to turn golden, flip your America covered bread on top of your other slice. Cover and let cook for an additional minute (so the melting cheese can cover the onions).
  6. Slice, serve, and enjoy.

Serve and Enjoy

Tips, Tricks, and Tweaks

  • American cheese melts REALLY well…but it melts better if you buy a block from the deli and slice it yourself (that way, it doesn’t have a bunch of preservatives…which change how the cheese melts). Since it melts so well, this is why I often include a layer of American cheese in my grilled cheese recipes…it acts as a delicious, melty glue to keep you sandwich together…and this way, you can use other cheeses that don’t melt as well yet have other flavors!
  • These onions last well in the fridge…and are yummy in breakfast skillets and breakfast burritos…so I usually make extra and save them for later!

Adult Grilled Cheese With Cinnamon Caramelized Onions

Recipe details

  • 2  Sandwiches
  • Prep time: 25 Minutes Cook time: 10 Minutes Total time: 35 min
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  • 4 slices of good bread
  • Fontina cheese, 2 - 4 ounces
  • American cheese (buy a block from the deli; see notes), 2 - 4 ounces

Cinnamon Caramelized Onions

  • ½ Large or 1 medium onion
  • 1 Tbsp unsalted butter
  • Kosher salt
  • ½ tsp cinnamon

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  • Lori Ward-Laatsch Lori Ward-Laatsch on Sep 03, 2021

    If you want to make a big batch of carnalized onions try the slow cooker method it works great no pan sitting just make sure you will be home for more than about 12 hours. I put them in at night, on a weekend, and then when I get up I check to see if they need more time, I found that in the morning if I removed the lid it help if you find a lot water that accumulated over night, you don't always have water I think it depends on the onions some had more water content or something. But they always turn out yummy.

    • Jessica Jessica on Sep 04, 2021

      Oh nice! Great tip! Thank you for sharing 🙂