Butter Burgers

Steps

1. Melt 2 tablespoons butter in a large cast-iron skillet over medium heat. Add onion and 1/4 teaspoon salt; cook, stirring, until tender, 2-3 minutes. Transfer to a bowl.
2. Toast the buns in the same skillet over medium heat until golden but still soft. Spread with 3 tablespoons butter.
3. Form the beef into four 4-inch patties. Season both sides with remaining 1 teaspoon salt and the pepper.
4. Melt 1 tablespoon butter in the same skillet over medium-high heat. Cook the burgers 2-3 minutes per side for medium doneness.
5. In the last minute of cooking, top each patty with a slice of cheese and let it melt.
6. Place patties on bottom buns. Top each with about 1/2 tablespoon butter and 3 tablespoons cooked onions.
7. Add bun tops and serve with pickle spears.