Place beef in slow cooker, and cover with onion. In a medium bowl, stir together ketchup, Worcestershire sauce, brown sugar, salt, paprika, mustard, V-8, Onion Soup Mix and 1 cup water. Pour mixture over beef and onions.
Cover, and cook on Low for 9 to 10 hours, or until meat is tender.
Mix 1/4 cup water with flour to form a paste, and stir into goulash. Cook on High for 10 to 15 minutes, or until sauce thickens. Serve over rotini pasta prepared to package directions with Garlic Bread.