Caramelized Onion Gruyère Cheese (Printable)

Melted Gruyère and sweet caramelized onions between buttery toasted bread create a cozy, flavorful dish.

# 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, for spreading
09 - 5 ounces Gruyère cheese, grated
10 - Caramelized onions prepared above

# Directions:

01 - Melt butter in a large skillet over medium-low heat. Add sliced onions, salt, and pepper; cook, stirring occasionally, for 25 to 30 minutes until deeply golden. Stir in sugar and balsamic vinegar if using; cook 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 on a work surface and evenly distribute half the grated cheese over them. Spoon caramelized onions atop the cheese, then sprinkle with remaining cheese. Top each with the remaining bread slices, butter-side up.
03 - Heat a nonstick skillet or griddle over medium heat. Place sandwiches in the skillet and cook 3 to 4 minutes per side, pressing lightly, until bread is golden and cheese melts. Lower heat as needed to prevent burning before cheese melts.
04 - Slice sandwiches in half and serve immediately.

# Expert Hints:

01 -
  • The caramelized onions do something magical—they become sweet, complex, and nothing like the raw onion you started with.
  • Gruyère melts into silky richness that turns a simple grilled cheese into something you'd serve to guests without hesitation.
  • The whole thing takes less time than you'd think, mostly just waiting while the onions do their thing.
02 -
  • The onions need to caramelize slowly—rushing them over high heat will just burn them brown instead of coaxing out their natural sweetness.
  • Don't flip your sandwich more than once, and if the bread is browning too fast before the cheese melts, lower the heat and give it more time.
03 -
  • Use a spatula to press down gently on your sandwich as it cooks—this helps the cheese melt evenly and creates a better seal between the bread and the filling.
  • If you're making two sandwiches at once and the first one finishes before the second, keep the finished sandwich in a warm oven so the cheese stays soft while you cook the second.
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