Steakhouse Burger with A1 Sauce | Chopped

Ingredients

• 1 1/2 pounds ground beef, 80/20
• 1 teaspoon kosher salt
• 1/2 teaspoon black pepper, freshly ground
• 1 tablespoon unsalted butter
• 1 yellow onion, thinly sliced
• 4 slices sharp cheddar cheese
• 4 hamburger buns, split
• 1/3 cup A1 steak sauce
• 4 leaves lettuce
• 1 tomato, sliced
• 1 tablespoon vegetable oil