Serve this rich beef stew over egg noodles on day two.
Season steak with salt and pepper. Heat oil in a large pot over medium-high heat. Cook steak in batches, turning, until browned, about 5 minutes. Transfer to a cutting board; cut into bite-size pieces.
Add onions and vinegar to pot; cook, stirring occasionally, until onions are soft, about 5 minutes. Stir in tomato paste and spices; cook, stirring, 1 minute. Add broth and potatoes; bring to a gentle boil and cook until potatoes are tender, about 30 minutes.
Return steak to pot, along with any juices. Cook until warmed through. Season with salt and pepper. Reserve half of stew for next day; serve remainder with sour cream, parsley, and more pepper.