In 5-quart Dutch oven over medium-low heat, in hot lard or shortening, cook onions, green pepper and garlic just until onion is tender, about 10 minutes, stirring occasionally.
Add water, beef, heart, paprika, salt, red pepper and caraway seed; heat to boiling. Reduce heat to low; cover and simmer 1-1/2 hours or just until meat is fork-tender.
Add potatoes; cover and cook 10 minutes longer or until potatoes are tender.
Drain liquid from tomatoes and add to mixture in Dutch oven. With small knife, coarsely chop tomatoes; stir into mixture.
Cook soup just until heated through.
Ladle into warm soup plates and serve at once.