Finely dice the bacon. Peel and finely dice the onions. Coarsely crush 1 tsp. caraway in a mortar.
Heat the oil in a wide saucepan. Fry bacon and onions for about 3 minutes while turning. Add vinegar, bring to the boil and remove the pot from the heat. Add cabbage and caraway and mix well. Fill into a bowl, let cool down a little and knead well with your hands. Season to taste with salt, pepper and 2 tablespoons of sugar. Let the salad cool down and put it in a covered place overnight.
Clean and wash spring onions and cut into fine rings. Season salad again with salt and sugar. Sprinkle with spring onions.