Wilt onion in lard in a heavy Dutch oven. Add pork, mix well, and cook covered for 5 minutes.
Add paprika, then the tomato purée; mix well. Add just enough water to cover everything. Cook over very low heat till meat is almost done.
Squeeze sauerkraut well. Add it to the meat with the caraway seeds, and cook for another 10 to 15 minutes. Salt should be added only at this point if you think, after tasting, that it is needed.
Spoon sour cream on top, and serve.
I. Mix 1cup sour cream with 1tablespoon flour. Mix it into the casserole 10 minutes before it is finished.
II. Dribble Paprika Essence on top, or save out 2tablespoons of the pork gravy and spread that over the top.
III. Carmelize 1tablespoon sugar in a pot, then add sauerkraut; mix well. Cook sauerkraut for 1 hour before adding it to the pork stew.
IV. If you want to cook this dish in the Hungarian peasant style, get fatty pieces of pork belly with the pork skin on; boned knuckle cut into pieces; ribs cut to small pieces. Use these to make the pörkölt.
V. By cooking the meat completely at the end of Step 1, you would have pork pörkölt (disznópörkölt).
VI. Boor people make this without meat. Sprinkle 3tablespoons flour on the sauerkraut 10 minutes before it is cooked, and mix well. It tastes surprisingly good.