Caramelized Onion Gruyère Cheese (Printable)

Golden grilled bread with nutty Gruyère and deeply caramelized onions for rich flavor and texture.

# What You'll Need:

→ Caramelized Onions

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

→ Sandwich

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

# Method:

01 - Melt 2 tablespoons of butter in a large skillet over medium-low heat. Add sliced onions, salt, and pepper, then cook, stirring occasionally, for 25 to 30 minutes until deeply golden. If desired, stir in sugar and balsamic vinegar, cooking 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, evenly distribute half the grated Gruyère over them, then layer with caramelized onions followed by the remaining cheese. Close sandwiches with remaining bread slices, butter-side up.
03 - Heat a nonstick skillet or griddle over medium heat. Cook sandwiches for 3 to 4 minutes per side, pressing gently, until bread is golden brown and cheese is melted. Reduce heat if bread browns before cheese melts.
04 - Slice sandwiches and serve immediately to preserve optimal texture and warmth.

# Expert Pointers:

01 -
  • The deep sweetness from slow cooked onions balances perfectly with Gruyères nutty complexity
  • One bite explains why this sandwich appears on bistro menus everywhere
02 -
  • Rushing the onions is the biggest mistake people make with this recipe
  • Low and slow cooking develops sweetness you cannot achieve any other way
  • The butter on the bread must be softened or it will tear and create uneven spots
  • Pressing too hard while cooking squeezes out the cheesy center
03 -
  • Make a double batch of onions and keep them in the refrigerator for up to a week
  • Adding fresh thyme leaves during the last 5 minutes of onion cooking creates restaurant level depth
  • Mayonnaise mixed into the butter creates an extra golden, crispy crust
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