Peel and chop the onion. Dab meat dry and cut into slices. Heat the oil in a flat frying pan with lid. Fry the meat for 2-4 minutes on each side. Season and remove.
Boil up about 2 l salted water. Sauté onion in hot frying fat. Add sauerkraut and ajvar. Season with salt, pepper and 1 pinch of sugar. Cover and stew for about 15 minutes.
Cook the spaetzle in the boiling salted water for about 2 minutes. Wash parsley, shake dry, pluck off leaves and chop. Drain the spaetzle and let it drain.
Add meat to the sauerkraut and heat. Season to taste with salt and pepper, sprinkle with parsley and serve with spaetzle. Crème fraîche tastes good with it.