Pour off the sauerkraut juice, reserving the juice, chop it up and set aside. Saute the onions in the oil or butter until golden. Add the drained, chopped sauerkaraut, cabbage, bouillon cube, and sauerkraut juice. Cook over low heat, uncovered, until the liquid evaporates, stirring often. Add the pepper, stir and cool. Chop once or twice in the processor or run through a meat grinder. NOTE: This stuffing is also excellent in Pyrizhky or crepes. Keeps well in the refrigerator.