Place a Dutch oven or large soup pot over medium-high heat.
Add the ground beef, chopped white onion, and minced garlic to the pot.
Cook, stirring and crumbling the beef, until the meat is fully browned and no longer pink.
Drain off any excess fat from the pot.
Add the taco seasoning to the browned beef mixture.
Stir until the beef is evenly coated with the seasoning.
Pour in the beef stock or beef broth.
Add the frozen corn, rinsed and drained black beans, petite diced tomatoes with juice, tomato purée, lime juice, salt, and uncooked rice.
Stir thoroughly to combine all ingredients and distribute the rice evenly.
Bring the soup mixture to a boil.
Once boiling, reduce the heat to a simmer.
Cover the pot with a lid.
Simmer for 20 to 25 minutes, or until the rice is tender.
Stir occasionally during cooking to prevent the rice from sticking to the bottom of the pot.
Once the rice is fully cooked, stir in the fresh cilantro.
Taste and adjust seasoning if needed.
Ladle the soup into serving bowls.
Serve warm with shredded cheese, sour cream, lime wedges, additional cilantro, and tortilla chips, if desired.