Caramelized Onion & Apple Grilled Cheese
Crispy sourdough, caramelized onions, sweet-and-tart apples and melty sharp cheddar make this adult grilled cheese an instant comfort classic.
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There’s something undeniably comforting and nostalgic about a grilled cheese sandwich – gooey cheese, crisp golden bread and buttery goodness in every bite. But sometimes you want something a little more grown up. That’s where this Caramelized Onion & Apple Grilled Cheese enters the chat.
This is an adult grilled cheese that brings the sweet, savory, tangy and crispy to every single bite. Plus, it’s a fall favorite thanks to caramelized onions, tart and sweet apples and sharp cheddar cheese.
Why this recipe works
I’ve tested a few variations of this recipe over the years, even trying brie in place of cheddar. While delicious, brie didn’t deliver the same melty magic you get from the classic apple and cheddar pairing. It just can’t be beat.
Quickly caramelizing the onions brings deep sweetness that balances the tart bite of thinly sliced Fuji apples. And here’s the secret: swapping butter for mayonnaise on the bread gives the sandwich an irresistibly crispy exterior.
Ingredients You’ll Need
- 1 tablespoon olive oil
- ½ medium onion, sliced thin
- 1 Fuji apple, sliced thin
- 1 pinch salt
- 2 tablespoons mayonnaise
- 4 slices sourdough (from a bakery loaf, sliced to preference)
- 4 slices cheddar cheese
How to Make Apple Grilled Cheese
Caramelize the onions. Heat olive oil in a skillet over medium heat. Add sliced onion and cook for about 10 minutes, stirring occasionally, until golden and softened. Sprinkle in a pinch of salt.
Add the apples. Stir in thinly sliced Fuji apple – you want to get them as paper thin as possible – and cook for another 3 to 4 minutes, just until the apples soften and start to release their juices.
Assemble the sandwiches. Spread mayonnaise on one side of each slice of sourdough. On the inside of one slice of bread, layer: cheddar cheese, caramelized onion and apple mixture, another slice of cheddar and the other piece of bread.
Cook the grilled cheese. Place sandwiches mayonnaise side down in a skillet over medium heat. Tent loosely with foil or cover with a lid to help the cheese melt. Cook for 4 to 5 minutes per side, lowering the heat if needed to prevent burning.
Serve and enjoy. The bread should be golden brown and crispy, with cheddar fully melted and gooey inside. Slice and serve warm.
Recipe Tips & Substitutions
- Mayonnaise vs. butter: Mayonnaise spreads more easily and creates a crispier, golden crust, but butter will work in a pinch.
- Cheese swaps: Try adding some shredded gruyere or cream cheese along with the cheddar for extra creaminess.
- Bread options: Sourdough is ideal because it’s sturdy, but a rustic country loaf or multigrain can also work.
- Apples & onions: Cooked apples create a softer bite, while raw apples keep things crunchy. Both will work. Raw onions, however, overpower the flavor, so stick with caramelized.
Frequently Asked Questions
Yes! Simply skip the onions for a more classic apple grilled cheese.
Fuji is a great balance of sweet and tart, but Honeycrisp, Pink Lady, or Granny Smith all make excellent choices.
You certainly can, but bakery sourdough is sturdier and holds up better to the weight of caramelized onions and apples.
Sharp cheddar is the classic choice. For variations, try gouda, Havarti, cream cheese or a mild brie layered with cheddar.
Keep the heat at medium or lower, and tent the pan with foil or a lid to trap heat and help melt the cheese faster.
Why You’ll Love This Adult Grilled Cheese
This isn’t just any sandwich, it’s comfort food elevated. The caramelized onions and tender apples add layers of flavor that turn a childhood favorite into something crave-worthy for adults, too. Pair it with a simple green salad or a warm bowl of butternut squash soup, and you’ve got the perfect cozy meal.
Caramelized Onion & Apple Grilled Cheese
Ingredients
- 1 tablespoon olive oil
- ½ medium onion, thinly sliced
- 1 small Fuji apple, thinly sliced
- 1 pinch salt
- 2 tablespoons mayonnaise
- 4 slices sourdough, from a bakery loaf
- 4 slices sharp cheddar cheese
Instructions
- Heat olive oil in a skillet over medium heat. Add onions and cook for about 10 minutes, stirring occasionally, until golden and just caramelized. Sprinkle with salt.
- Add sliced apple and cook for 3 to 4 minutes, until softened and tender. Remove from heat.
- Spread mayonnaise on one side of each slice of bread.
- On the uncoated side, layer a slice of cheddar, the onion and apple mixture, another slice of cheddar, then top with bread.
- Place sandwiches in a skillet over medium heat. Tent loosely with foil or cover with a lid to help the cheese melt. Cook 4 to 5 minutes per side, lowering heat as needed to prevent burning.
- When bread is golden and crispy and cheese is fully melted, remove, slice and serve immediately.
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