Sauté onion in butter over low heat until soft. Add cabbage to onion, lightly salt, and stir well. Cover. Sweat cabbage mix until very soft. (Add a small amount of water, only if necessary.) Stir occasionally. Add sliced apple and continue the sweating process until all is very soft. Remove from heat. Mash. Add vinegar, and stir well. Season to taste, and serve. 4-6 servings.
*The sweating process requires a little patience, but all the ingredients are cooked in their own juices, which improves flavor and color.
This recipe is from Jeanne Irwin, Lynnea Stadelmann's mother. "Mama" is the mother of a German friend of Jeanne's, and the one who provided the recipe.