Ingredients

• 1 pound ground beef
• 1 pinch salt and ground black pepper to taste
• 2 tablespoons butter
• 1 onion , sliced
• 6 slices dark rye bread
• 3 slices American cheese
• 3 slices Swiss cheese

Instructions

1. 1 Preheat an outdoor grill for medium heat and lightly oil the grate.
2. 2 Pat out three 1/3-pound hamburger patties, pressing each patty down with your index and middle fingers to get a nice, flat burger instead of a ball. Season patties on both sides with salt and pepper.
3. 3 Cook on the preheated grill until no longer pink in the centers, 10 to 12 minutes, flipping halfway. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).
4. 4 Meanwhile, melt butter in a saucepan over low heat. Increase heat to medium-low, add onion, and saute until tender, 5 to 7 minutes.
5. 5 Place 3 slices of bread on the grill. Top each with a slice of American cheese, a cooked patty, sauteed onions, a slice of Swiss cheese, and the remaining bread. Grill sandwiches until cheese melts, about 1 minute per side.

Nutrition per serving