Pat beef cubes dry and season with salt and pepper. Heat 1 tbsp lard in a large Dutch oven over medium-high heat. Brown beef in batches without crowding, turning to sear all sides, about 3-4 minutes per batch. Transfer to a plate.

Reduce heat to medium. Add remaining lard, then onions and bell peppers. Cook, stirring often, until soft and translucent, about 8-10 minutes. Stir in garlic and cook until fragrant, 1 minute.

Remove pot from heat. Immediately stir in paprika and caraway seeds until vegetables are well coated. Return to low heat and cook for 30 seconds, stirring constantly. Be careful not to burn the paprika.

Stir in diced tomatoes with their juices, beef broth, and bay leaves. Return beef and any accumulated juices to the pot. Bring to a boil, then reduce heat to a low simmer. Cover and cook for 1.5 to 2 hours, until beef is fork-tender and reaches an internal temperature of at least 145°F (63°C).

Remove bay leaves. Stir in vinegar, then season with salt and pepper to taste. Ladle into bowls, sprinkle with parsley, and serve with a dollop of sour cream if desired.