In a medium bowl, mix the first 3 ingredients (beef through garlic). Form beef mixture into patties. Heat grill to medium-high heat and place burgers on the grill.
Cook for 10 minutes on each side, until burgers reach desired level of doneness.
In a large skillet, over medium heat, heat coconut oil. To the skillet, add the onion.
Season with sea salt and freshly ground black pepper to taste and cook for 5 minutes, until onions are tender.
Place burgers on lettuce leaves and top with sautéed onion.