Chop the onion finely and fry in large saucepan until the onions are golden. Add the sugar and caramelize. Add the wine and reduce by half. Cut the red cabbage into thin strips and add to the saucepan. Add the apples, salt and pepper to taste and stir. Cook until the cabbage softens. Taste and adjust seasoning.
It is also customary to add a quarter cup of vinegar to the wine and reduce them together, and two cloves when adding cabbage to the pot. It's just amazing, sweet and sour dish with an addictive taste. In this case because the cabbage is served with the Sauerbraten, I find it less suitable but for those of you who love to experience new flavors feel free to experiment!