How to Make It
In a large Dutch oven, cook bacon over moderate heat until crisp, about 7 minutes. Using a slotted spoon, transfer bacon to a plate, leaving fat in pan.
Season beef with salt and pepper. In batches, add beef to pot, and cook in bacon fat over moderately high heat until browned all over, about 5 minutes per batch. Using a slotted spoon, transfer beef to plate with bacon.
Add 1/4 cup of water and onions to pot. Cook, stirring with a wooden spoon and scraping up browned bits, until all liquid is evaporated and onion is softened, about 6 minutes. Add paprika, tomato paste, and caraway seeds; cook, stirring, for 1 minute.
Add 7 cups of water and 1 tablespoon of the apple cider vinegar; return the meat and any accumulated juices to the pot. Bring the goulash to a boil, cover partially, and simmer over low heat for 11/2 hours.
Add potatoes and bell pepper to pot, and simmer, partially covered, over low heat until beef is very tender and sauce is slightly thickened, about 1 hour.
Stir in fish sauce, if using, and remaining 1 tablespoon apple cider vinegar. Season with salt and pepper. Ladle into bowls and serve with sour cream and rye bread.