Ingredients

Start to finish: 40 minutes
Servings: 2

1 tablespoon butter
1 tablespoon extra-virgin olive oil
1 medium red onion, thinly sliced
Kosher salt and freshly ground black pepper, to taste
Splash of water
1 teaspoon balsamic vinegar
3 tablespoons mayonnaise
1 teaspoon whole-grain mustard
1 large clove garlic, finely minced or pressed
1/2 teaspoon lemon juice
4 slices rustic white, sourdough or multigrain bread
2 slices cold meatloaf, about 1/2 inch thick
4 slices Monterey Jack cheese
2 leaves romaine lettuce, center rib removed, folded and trimmed to fit the bread

Directions

In a nonstick skillet over medium-high heat, combine the butter and olive oil, heating until the butter has melted. Add the onion slices and saute until they start to brown, about 10 minutes. Season with salt and pepper.

Add a splash of water to deglaze the pan, then lower the heat to medium and continue cooking until the onions are soft and caramelized, about another 15 minutes. If the pan gets dry, add a bit more water.

Stir in the balsamic vinegar and remove from the heat. Let the onions cool to room temperature. The onions can be refrigerated for later use. If so, let warm at room temperature for 30 minutes before using.

Meanwhile, in a small bowl whisk together the mayonnaise, mustard, garlic and lemon juice. Season with salt and pepper, then set aside. This also can be prepared ahead and refrigerated.

To assemble the sandwiches, lightly toast the bread. Let the bread cool for a minute, then spread some of the mayonnaise mixture on all four slices.

Top two of the bread slices each with a slice of meatloaf. Place half of the onions over each meatloaf slice, then top each sandwich with two slices of cheese, a leaf of lettuce and a final slice of bread.

If desired, trim the ingredients to fit neatly between the bread slices. Cut in half on the diagonal and serve.

Nutrition information per serving: 873 calories; 579 calories from fat; 64 g fat (25 g saturated; 0 g trans fats); 130 mg cholesterol; 42 g carbohydrate; 34 g protein; 4 g fiber; 1,375 mg sodium.