Caramelized Onion Gruyère Cheese (Printable Version)

Golden bread with melted Gruyère and sweet caramelized onions in a savory, buttery sandwich.

# What You'll Need:

→ Caramelized Onions

01 - 2 medium yellow onions, thinly sliced
02 - 2 tablespoons unsalted butter
03 - 0.5 teaspoon kosher salt
04 - 0.25 teaspoon freshly ground black pepper
05 - 0.5 teaspoon sugar (optional)
06 - 1 teaspoon balsamic vinegar (optional)

→ Sandwich

07 - 4 slices rustic sourdough or country bread
08 - 2 tablespoons unsalted butter, softened
09 - 5 ounces Gruyère cheese, grated
10 - Caramelized onions (prepared above)

# How-To Steps:

01 - Melt 2 tablespoons butter in a large skillet over medium-low heat. Add sliced onions, salt, and black pepper. Cook, stirring occasionally, for 25–30 minutes until onions are deeply golden and caramelized. If using, stir in sugar and balsamic vinegar and continue cooking for 2–3 minutes. Remove from heat.
02 - Lay out bread slices and spread one side of each with softened butter. Place two slices butter-side down, evenly distribute half the grated Gruyère on top, then spoon caramelized onions over the cheese. Top with the remaining Gruyère and close each sandwich with the other bread slices, butter-side up.
03 - Heat a nonstick skillet or griddle over medium heat. Place sandwiches in the skillet and cook for 3–4 minutes per side, pressing gently, until the bread is golden brown and cheese is melted. Reduce heat if bread browns too quickly before cheese melts.
04 - Slice sandwiches and serve immediately.

# Expert Advice:

01 -
  • The cheese gets impossibly melty while the bread toasts to this perfect golden-brown crispness.
  • Those caramelized onions have a sweetness and depth that transforms a grilled cheese into something that doesn't feel like leftover lunch.
  • You can make the onions ahead and still have dinner on the table in under 15 minutes.
02 -
  • Don't skip the low heat for caramelizing—high heat just dries out the onions instead of sweetening them.
  • If your bread is browning too fast, lower the heat before the cheese finishes melting.
  • Grating the cheese fresh rather than using pre-shredded makes a huge difference in how smoothly it melts.
03 -
  • You can caramelize the onions the day before and store them in the fridge, which means dinner is just 15 minutes away.
  • Don't press down too hard on the sandwich while it cooks—gentle pressure helps the cheese melt without squishing everything out the sides.
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