1 large sweet onion, sliced thin
1 teaspoon salt, divided
1 teaspoon black pepper, divided
2 hamburger patties 85 percent lean ground beef, about 5 oxen each
1 tablespoon unsalted butter, plus extra for buns
1 tablespoon vegetable oil
½ teaspoon sugar
2 slices American cheese
2 hamburger buns
Mix onions with ½ teaspoon salt, ½ teaspoon pepper, and sugar.
Season the burger patties with ½ teaspoon salt and ½ teaspoon pepper. Place on a plate.
Cut the hamburger buns in half and butter each side. Wrap in foil and heat in a 300-degree oven while you cook the burgers.
Melt butter with the oil in a 12-inch nonstick skillet over medium heat. Add the onions. Cook for 10 to 12 minutes, stirring occasionally, until the onions are browned and caramelized. Divide the onions in half. Place each half on the prepared burger. Press the opinion mixture down on the burgers with a large metal spatula.
Using the spatula, transfer burgers to the skillet onion side up and cook for 5 minutes. Carefully turn the burgers over, increase heat to high, and cook until well browned on the second side, about 5 minutes.
Remove the hamburger buns from the oven. Place one slice of American cheese on each bun bottom. Transfer burgers to buns, and add serve desired toppings.
Make a side salad or serve with sliced cucumbers and tomatoes topped with your favorite salad dressing.