Peel and dice the onions. Halve the peppers, clean and rinse under cold water and dry. Cut into narrow strips. Remove tubes and skin remnants from the swabbed liver and cut into 3 cm cubes.
Heat the margarine in a saucepan. Fry the onion cubes for about 3 minutes. Add the liver and fry for 3 minutes. Add the pepper strips and fry for 5 minutes. Season with salt and pepper. Dust the flour over it and pour in the meat broth while stirring. Let simmer for 5 minutes. Stir in the tomato paste and sour cream. Season with marjoram and season to taste.
Arrange in a preheated bowl and serve immediately.