-
1
Heat a grill to medium-high direct heat and lightly oil the grates using a paper towel soaked in canola oil or nonstick grilling cooking spray.
-
2
Spread a 16-inch-long piece of nonstick aluminum foil on a cutting board (or mist a piece of regular aluminum foil with nonstick cooking spray).
-
3
Top with the onions, 1/4 teaspoon each salt and pepper and 1 tablespoon water.
-
4
Bring two sides of the foil together, fold over twice to create a seal and then seal the remaining two ends.
-
5
Put on the grill and cook for 12 minutes, flipping once.
-
6
The onions should be tender with only a bit of charring.
-
7
Carefully open the top of the foil to let all the steam out and continue to cook the onions, tossing, until browned and lightly charred, 3 minutes longer.
-
8
Remove from the heat.
-
9
While the onions cook, mix the ketchup and mustard together in a small bowl.
-
10
Season with pepper and set aside.
-
11
Lightly toast the English muffins on the grill and place one top and bottom on each of 4 plates.
-
12
Spread some of the ketchup sauce on the bottom half of each muffin and top with a slice of tomato.
-
13
Divide the beef into 4 patties about 4 inches in diameter and just under 1/2-inch thick.
-
14
Sprinkle with a total of 1/2 teaspoon salt and 1/4 teaspoon pepper.
-
15
Place the burgers on the grill.
-
16
Cook until the edges of the burgers are browning, 3 to 5 minutes, and then flip.
-
17
Brush the burgers with the remaining ketchup sauce and evenly top with the shredded cheese.
-
18
Cover the burgers with the grill lid or a large heatproof bowl and continue to cook until the cheese has melted and the burgers are still a bit pink on the inside, about 3 minutes more.
-
19
Put one burger on top of the assembled muffin bottom and top with some of the grilled onions and the top of the muffin.
-
20
Serve with pickles if desired.
