Heat 1 tablespoon oil in a large ovenproof nonstick skillet over medium heat. Add the turnips, onion and the remaining 1/4 teaspoon salt. Spread and pat the mixture into an even layer; cook, without stirring, for 2 minutes. Then stir the mixture and scrape up any browned bits. Pat the mixture back into an even layer and continue cooking, without stirring, for 2 minutes. Stir again, spread back into an even layer and cook until mostly golden brown, 2 to 4 minutes more. Transfer to a plate. Wash and dry the pan.