Cook the sweetpotatoes until fork tender, then mash until smooth.
Add the eggs and cinnamon to the mashed sweetpotatoes and mix until fully combined.
Preheat a waffle maker and lightly coat it with cooking spray if needed.
Spoon the sweetpotato mixture into the waffle maker and cook until the waffles are firm and lightly golden. These will serve as your burger buns.
While the waffles are cooking, season the lean ground beef with salt and form into burger patties.
Cook the patties in a hot skillet until they reach your preferred level of doneness.
Assemble the burger by placing the beef patty between two sweetpotato waffles and topping with lettuce, tomato, pickles, special sauce, or any additional toppings you enjoy.
Serve immediately and enjoy.