Juicy grilled cheeseburgers

Ingredients:

• 1 medium red onion, thinly sliced
• 2 tbsp. ketchup
• 2 tbsp mustard
• 4 whole grains English muffins, cut horizontally in half
• 1 medium ripe tomato, core removed and cut into 4 thick slices
• 450 g ground beef, 10% fat
• 55g reduced-fat sharp cheddar, grated (about 1/2 cup)
• Pickled cucumbers, for serving (optional)

Preparation:

1. Preheat grill to medium-high heat and lightly coat grates with a paper towel dipped in vegetable oil or spray with cooking spray.
2. Line a 16-inch sheet of nonstick aluminum foil on a cutting board (or spray a sheet of regular aluminum foil with cooking spray). Arrange the onions on top, sprinkle with 1/4 teaspoon each of salt and black pepper, and drizzle with 1 tablespoon of water. Bring the two sides of the foil together, fold twice to form a tight seam, and then seal the remaining two ends. Place on the grill and grill for 12 minutes, turning once. The onions should be tender with a few charred spots. Carefully open the top of the foil to release steam, and continue grilling the onions, stirring, until golden brown and lightly charred, another 3 minutes. Remove from heat.
3. While the onions are frying, mix the ketchup and mustard in a small bowl. Season with pepper.
4. Lightly toast the English muffins on the grill and divide them into top and bottom halves on 4 plates. Spread some of the sauce on the bottom halves of the muffins and top with tomato slices.
5. Form the ground meat into 4 patties, about 4 inches in diameter and just under 1/2 inch thick. Season with a total of 1/2 teaspoon salt and 1/4 teaspoon black pepper. Place the patties on the grill. Grill until the edges are golden brown, 3 to 5 minutes, then turn over. Brush them with the remaining ketchup sauce and sprinkle evenly with grated cheese. Cover with the grill lid or a large ovenproof bowl and continue grilling until the cheese is melted. The patties should still be slightly pink on the inside, about 3 more minutes.
6. Place one patty on a tomato bun and top it with a little fried onion, then top with the top half of an English muffin. Assemble the remaining burgers and serve with pickles, if using.