Bistro Cheeseburgers

1 1/2 pounds ground beef
Vegetable oil 4 slices sweet onion — 1/2 inch thick
4 crusty rolls — split, toasted
4 romaine lettuce leaves
4 tomato slices — 1/2 inch thick
8 slices Swiss cheese
1/4 cup mayonnaise
1 tablespoon Dijon mustard

In small bowl, combine the sauce ingredients (mayonnaise and Dijon mustard); set aside.

Shape ground beef into four 3/4″ thick patties. Lightly brush oil onto cut sides of onion. Place patties and onions on the grill with the setting at medium. Grill, uncovered, 13 to 15 minutes or until centers are no longer pink and onions are tender.

Season burgers with salt and pepper. Approximately 1 minute before burgers are done, top each burger with 2 slices of cheese.

Spread equal parts of sauce mixture on top half of each roll and line the bottom half of each roll with lettuce and tomato and top with cheeseburger and onion.

I like to butter the buns and place them on the warming rack until they start to turn brown. This adds to the flavor of the burgers.