Ingredients

2 lb Criollo ground steak
4 sweet onion slices (1/2")
Vegetable oil
8 slices Swiss process cheese food
1/4 cup mayonnaise
1 Tbsp Dijon-style mustard
4 crusty rolls, split, toasted
Romaine lettuce, tomato slices

1. Lightly shape ground beef into four 3/4" thick patties. Brush onion with oil.
    
2. Place patties in center of grid over medium, ash-covered coals. Place onion around patties. Grill, uncovered, 13 to 15 minutes to medium (160°F) doneness, until patties are not pink in center and juices show no pink color and onions are tender, turning occasionally. Season with salt and pepper. About 1 minute before patties are done, top each with 2 cheese slices.
    
3. Mix mayonnaise and mustard; spread on roll tops. Serve burgers and onion in rolls with lettuce and tomato.