Roast Beef Sandwich with Caramelized Onions

Up your sandwich game when you make these sweet, savory, completely satisfying roast beef sandwiches. Loaded with flavor, they make a hearty lunch or easy dinner. You will have leftover onions from this recipe -- use them as a garnish for bean soup or stirred into sour cream for a quick dip. This recipe makes 2 sandwiches.

PREP TIME: 10 minutes
COOK TIME: 30 minutes

Ingredients
For the caramelized onions:
1 large yellow or sweet onion, sliced
1 tablespoon olive oil
1 tablespoon butter
Salt, to taste

For the sandwich assembly:
4 slices good quality sourdough bread
2 tablespoons butter, divided
1/2 pound sliced roast beef
2 tablespoons mayonnaise
2 tablespoons whole-grain mustard
2 ounces sliced Swiss or jack cheese
10-12 slices pickles (sweet or dill)

Directions
Make the onions: Heat oil and butter in a large, heavy skillet to medium on the stove top. Add onions and stir to coat with the fat. Cook, stirring every few minutes, until the onions are softened, fragrant and a caramel brown color; the entire process should take about 20 minutes. Salt the last few minutes of cooking. Remove from heat and set aside onions on a plate or bowl.

Put the same skillet back onto the stove and add 1 tablespoon butter. Add 1 tablespoon of mayonnaise to each of 2 slices of bread and place in pan, mayo side up. Top bread slices with cheese, roast beef, pickles and a scoop of onions, distributing evenly amongst bread slices. Add mustard to the remaining two bread slices and place atop the sandwiches in the pan. Grill for 8-10 minutes, flipping once in the middle of cooking, or until bread is toasted and cheese is melted. Remove from heat, slice and serve immediately.