Peel and dice onion. In a pan, sauté onion in 1 tablespoon oil until softened. Stir in sauerkraut. Season with salt, pepper and allspice. Cover and cook about 30 minutes.
In another pan, sauté leberkäse until browned on both sides. Remove from pan and keep warm. Add remaining oil to the pan. Add marjoram leaves and sauté 1-2 seconds. Drain on paper towels.
Cut pineapple into pieces. In the last 10 minutes of cooking time, add pineapple to sauerkraut. Season to taste. Serve leberkäse topped with sauerkraut and garnish with fried marjoram leaves.