1Make high protein bone broth caramelized onions. Cook diced onions in butter until brown, then deglaze with beef bone broth until all liquid is evaporated.
2Add soy sauce for extra flavor and color.
3Mix ground beef with salt, pepper, garlic, and caramelized onions to form a patty.
4Make burger sauce by mixing light mayo, sugar free ketchup, sweet relish, caramelized onions, salt, garlic, and pepper.
5Toast bread slices with butter.
6Cook the burger patty in a pan until seared, adding a slice of cheddar cheese on top to melt.
7Assemble the burger by layering burger sauce on the toasted bread, adding the patty with melted cheese, and topping with the other bread slice and additional caramelized onions.