Cooking Instructions

• Add the butter to a rondeau or cast iron skillet and heat over medium heat. Once melted, add onions, season with salt, and mix.
• Cover and let onions stand for 5 to 6 minutes, then stir for 1 to 2 minutes until light brown.
• Turn heat to low-medium and stir every 6 to 8 minutes for 30 to 35 minutes until very dark brown. Deglaze with vinegar, season with salt, and stir.
• Form ground beef into 3 patties on a sheet tray lined with parchment paper.
• Slice the bread and shred the cheese.
• Heat a griddle or cast iron skillet to medium-high heat, about 375° to 400°.
• Season the top side of the burgers with coarse salt and freshly cracked black pepper.
• Drizzle 2 to 3 teaspoons of oil or butter onto the griddle.
• Place the patties seasoned side down and season the top side.
• Cook the burgers for 3 minutes untouched, then flip.
• Spread 2 teaspoons of softened butter on each side of the rye bread slices.
• Place the bread on the griddle and cook for 1 to 2 minutes until toasted, then flip.
• Once flipped, sprinkle ⅓ of shredded Swiss cheese on each slice and top with ⅓ of the caramelized onions.
• Add the burger patty and top with the other toasted rye slice.
• Slice and serve.