Recipe: Grilled Gruyère and marinated onion sandwich

Total time: About 25 minutes, plus marinating time for the onions

Servings: Makes 2 sandwiches

Note: Adapted from Campanile chef-owner Mark Peel

1/2 cup Spanish or brown onion, very thinly sliced

1/4 teaspoon kosher salt

1/4 teaspoon freshly ground black pepper

1 tablespoon best-quality olive oil

1 tablespoon white wine vinegar

4 slices country white bread

4 tablespoons salted butter, melted

5 ounces Gruyère cheese, coarsely grated

4 teaspoons stone-ground mustard

1. In a small bowl, mix together the onion, salt, pepper, olive oil and vinegar. Cover and let sit for at least 1 hour.

2. Heat a cast-iron pan or griddle over low heat. Brush one side of each slice of bread with the melted butter. Place two slices of bread, butter-side down, on a cutting board. Spread half of the grated cheese evenly over the bread. Drain the excess liquid from the marinated onions and scatter them evenly over the cheese-topped slices. Distribute the remaining cheese evenly over the onions. Spread the mustard over the unbuttered sides of the remaining 2 slices of buttered bread. Place these, mustard-side down, on top of the slices spread with cheese.

3. Using a spatula, place one of the sandwiches into the hot pan and weight with another heavy skillet or a steak weight. (If your pan is big enough, cook both sandwiches; otherwise, cook one at a time.) Cook until golden brown, about 3 to 4 minutes. Flip the sandwich and weight it with the pan or steak weight, and cook until golden brown, another 3 to 4 minutes.

4. Remove the sandwich to a cutting board and cut it in half or quarters. Serve immediately.

Each sandwich: 745 calories; 29 grams protein; 37 grams carbohydrates; 2 grams fiber; 55 grams fat; 29 grams saturated fat; 138 mg. cholesterol; 1,131 mg. sodium.