Cut the onion into fine cubes and the paprika into narrow strips. Cut the tomatoes into eighths. Heat the oil in a pan and fry the onion in it, add the crushed garlic and tomatoes. Let everything stew for about 5 minutes. Stir in the tomato paste and cream, season everything with salt, pepper, sugar and a little sage. Bring the sauce to the boil and season to taste. Keep the sauce warm.
Heat some of the butter in a pan. Add the paprika strips, season with salt and pepper, sauté and add to the sauce.
Cut the liver into strips and fry in the heated butter for approx. 4-5 minutes and season with salt and pepper. Now add the strips to the sauce.