Heat oil in a large saucepan over medium-high heat. Add onion, green pepper and red pepper; cook, stirring, until starting to soften, about 3 minutes.

Add beef, paprika, marjoram, caraway seeds, salt and pepper. Cook, stirring, until the beef is no longer pink, 3 to 5 minutes. Stir in broth, potatoes and tomatoes; bring to a boil. Reduce heat to maintain a simmer and cook, uncovered, stirring occasionally, until the potatoes are tender and the soup has thickened a bit, about 20 minutes.

Stir in vinegar.

Divide the soup among 4 bowls and garnish each with 1 tablespoon sour cream and ½ tablespoon parsley.