2 servings; can be doubled or tripled.
Mix first 5 ingredients in medium bowl. Add ground turkey and generous amount of pepper. Form mixture into two 1/2-inch-thick patties.
Pour thin layer of oil into heavy medium skillet over medium heat. Add patties. Cover and fry until just cooked through, about 3 minutes per side. Top each patty with cheese. Cover and cook until just melted. Transfer to plates. Top with onion slices and serve.