Heat 1 tablespoon oil in heavy medium skillet over medium- high heat. Add onions, sprinkle with salt, and sauté until tender and golden brown, stirring often, about 10 minutes. Reduce heat to medium and continue to sauté until very tender and well browned, about 15 minutes longer. Add wine and cook, stirring occasionally, until liquid is absorbed, about 5 minutes. DO AHEAD:Cool, cover, and chill.