Pat meat dry with a paper towel and rub with 2 tablespoons flour and salt. Heat oil in a large saucepan over medium-high heat. Brown meat on all sides. Add the sliced onions, cover and reduce heat to low. Cook for about one hour, adding a little water if necessary. Turn meat twice during the cooking process.
Meanwhile, place beetroots in a saucepan with water to cover. Bring to the boil over medium heat and cook until beetroots are tender. Drain, reserving liquid. Chop beetroots into cubes and add to the saucepan. Add prunes and beetroot water, cover and simmer for 5 minutes.
Remove pork to a serving plate. Mix 1 tablespoon of flour with soured cream. Pour into saucepan (used to cook the pork) and mix well, scraping the sides and bottom. Simmer until sauce thickens. Season with paprika and taste. Adjust seasoning if necessary.