Ingredients
4 tablespoons unsalted butter
1 pound yellow or Vidalia onions, peeled, halved, and thinly sliced
Kosher salt and black pepper to taste
2 teaspoons sherry, red-wine, or white-wine vinegar (optional)
4 ounces Gruyère cheese, grated
4 slices bread (no wider than ½-inch thick)
Instructions
- In a large skillet over medium-high heat, melt 2 tablespoons of butter. Add onions, season with salt and pepper, cover, and cook for 3–5 minutes until softened.
- Uncover, reduce heat to medium-low, and continue cooking for 20–25 minutes, stirring occasionally until onions are deep golden brown. Add water as needed to prevent burning. Deglaze with vinegar if using and cook for 1 minute more. Transfer onions to a bowl and season to taste.
- Stir grated Gruyère into the warm onions until well combined.
- Place two slices of bread on a surface and pile half of the onion-cheese mixture on each. Top with remaining bread slices and press gently.
- In the same skillet, melt 1 tablespoon butter over medium heat. Add sandwiches and cook until bottoms are golden brown, 3–4 minutes. Flip, add remaining butter, press down, and cook another 3–4 minutes until cheese is melted and bread is crisp.
- Serve immediately while hot and gooey.
Notes
- Caramelized onions can be made ahead and frozen for convenience.
- Deglaze with bourbon instead of vinegar for added sweetness.
- Try adding chopped dates to onions for a unique twist.
- Prep Time: 20 minutes
- Cook Time: 25 minutes
- Category: Sandwich
- Method: Stovetop
- Cuisine: American
- Diet: Vegetarian
Nutrition
- Serving Size: 1 sandwich
- Calories: 520
- Sugar: 5g
- Sodium: 580mg
- Fat: 32g
- Saturated Fat: 19g
- Unsaturated Fat: 11g
- Trans Fat: 1g
- Carbohydrates: 35g
- Fiber: 3g
- Protein: 19g
- Cholesterol: 90mg
