Caramelized Onion Gruyère Cheese (Printable Version)

Melted Gruyère and caramelized onions layered on golden buttered sourdough make a rich, savory melt.

# What You'll Need:

→ Caramelized Onions

01 - 2 medium yellow onions, thinly sliced
02 - 2 tbsp unsalted butter
03 - 0.5 tsp kosher salt
04 - 0.25 tsp freshly ground black pepper
05 - 0.5 tsp 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)

# Directions:

01 - Melt 2 tablespoons unsalted butter in a large skillet over medium-low heat. Add the sliced onions, kosher salt, and black pepper. Cook, stirring occasionally, for 25 to 30 minutes until onions become deeply golden and caramelized. Optionally stir in sugar and balsamic vinegar, cooking for an additional 2 to 3 minutes. Remove from heat.
02 - Lay out the bread slices and spread one side of each with softened butter. Arrange two slices butter-side down on a work surface. Evenly distribute half the grated Gruyère over these. Spoon caramelized onions atop the cheese, then cover with the remaining Gruyère. Close each sandwich with a buttered slice, butter-side up.
03 - Heat a nonstick skillet or griddle over medium heat. Place the sandwiches in the skillet and cook for 3 to 4 minutes per side, pressing gently, until the bread is golden brown and the cheese fully melts. Adjust heat lower if bread browns too quickly before the cheese melts.
04 - Slice sandwiches and serve immediately, optionally paired with a crisp green salad or tomato soup.

# Expert Tips:

01 -
  • Caramelized onions turn sweet and almost jam-like, making every bite taste more elegant than it has any right to.
  • Gruyère melts into creamy depths that regular cheese just doesn't reach, making this feel like something you'd order out but actually made yourself.
  • It comes together faster than you'd think once the onions are done, so you can have something restaurant-worthy on the table in under an hour.
02 -
  • Caramelized onions are not the same as sautéed onions—rushing them defeats the whole purpose, so patience is the real ingredient here.
  • If your bread is browning before the cheese inside is melted, simply lower the heat slightly and cover the skillet with a lid for the last minute or two so steam helps melt the cheese through.
03 -
  • Grate your Gruyère fresh rather than using pre-shredded cheese—it melts more smoothly and distributes more evenly through the sandwich.
  • Make your caramelized onions ahead of time and store them in the fridge for up to four days; they're actually better the next day as flavors meld together.
Go Back