Heat a cast iron pan over medium high heat. You can also preheat a grill to 400 degrees instead.
Mix together the turkey, onion, oil, salt, and pepper.
Form into 4 patties.
Place the patties in the pan and cook for 4 to 5 minute per side or until desired doneness.
To serve, place romaine leaves on each burger bun and place burger on top.
Add some sliced avocado and desired accompaniments.