Place the pork roast in the bottom of a large slow cooker, fat side up if it has a cap of fat.
Scatter the sliced onion evenly over and around the pork roast in the slow cooker.
In a medium bowl or measuring pitcher, stir together the jarred sauerkraut (including all the juice), the applesauce, and the caraway seeds until everything is loosely combined.
Pour the sauerkraut mixture evenly over the pork roast in the slow cooker, making sure the meat is mostly covered with sauerkraut and liquid.
Cover the slow cooker with the lid and cook on LOW for 8 to 10 hours, or on HIGH for 4 to 5 hours, until the pork is very tender and easily pulls apart with a fork.
Once cooked, use two forks to gently pull the pork into large chunks or shreds right in the slow cooker, mixing it with the sauerkraut and onions.
Taste and add a little salt and black pepper if needed.
Ladle the pork and sauerkraut into shallow bowls or onto plates, making sure everyone gets some of the tangy juices. Serve hot with your favorite hearty sides.
