Slice and butter 6 pieces of rye bread, ensuring one side of each is generously coated.

In a bowl, combine ground beef with sea salt, black pepper, and onion powder. Form patties.

Heat a nonstick skillet over medium-high heat. Cook patties for 2-3 minutes on each side until browned.

In a bowl, whisk together mayonnaise and ketchup. Mix in bacon bits, sweet relish, and white sugar.

In another skillet, lay one slice of butter-side down; spread sauce on three unbuttered slices. Layer patties and cheeses.

Top with another buttered slice and cook until golden brown and cheese melts, flipping halfway through.