Caramelized Onion Gruyère Cheese (Printable)

Buttery golden bread filled with melted Gruyère and sweet caramelized onions for a rich, savory meal.

# What You Need:

→ Caramelized Onions

01 - 2 medium yellow onions, thinly sliced
02 - 2 tbsp unsalted butter
03 - 1/2 tsp kosher salt
04 - 1/4 tsp freshly ground black pepper
05 - 1/2 tsp granulated sugar (optional)
06 - 1 tsp balsamic vinegar (optional)

→ Sandwich

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

# How to Make It:

01 - Melt 2 tablespoons of butter in a large skillet over medium-low heat. Add sliced onions, salt, and pepper. Cook, stirring occasionally, for 25 to 30 minutes until onions turn deeply golden and caramelized. Stir in sugar and balsamic vinegar if using and cook for an additional 2 to 3 minutes. Remove from heat.
02 - Spread softened butter on one side of each bread slice. Place two slices butter-side down, then evenly distribute half the grated Gruyère over them. Spoon caramelized onions on top, followed by the remaining Gruyère. Cover with the remaining bread slices, butter-side up.
03 - Heat a nonstick skillet or griddle over medium heat. Place sandwiches in skillet and cook for 3 to 4 minutes per side, pressing gently, until bread is golden brown and cheese melts. Lower heat if bread browns too quickly before cheese melts.
04 - Slice sandwiches and serve immediately while warm.

# Expert Tips:

01 -
  • Those caramelized onions taste like you've been cooking for hours, but it's honestly just patience and butter doing the work.
  • Gruyère melts into this creamy, almost nutty heaven that makes everything else taste better.
  • It's simple enough for a weeknight but fancy enough that you won't feel guilty taking your time with it.
02 -
  • Medium-low heat and patience are the only real requirements for caramelizing onions; rushing them with higher heat makes them brown unevenly and taste bitter.
  • Grate your cheese fresh and don't skip it—pre-shredded cheese has cellulose powder that prevents it from melting into that silky texture you're after.
  • Let your butter soften at room temperature before spreading; cold butter tears the bread and won't distribute evenly.
03 -
  • If your cheese isn't melting by the time your bread is golden, lower the heat and cover the skillet with a lid for 30 seconds—the trapped steam does the work without burning anything.
  • Make your caramelized onions ahead of time; they actually taste better the next day and keep your actual sandwich assembly to five minutes.
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