Warm the pot: Set a large pot or Dutch oven over medium heat. Add olive oil if using lean meat.
Brown the meat: Add ground beef and cook, breaking it up with a spoon, until no longer pink, about 5–7 minutes. Season with a pinch of salt and pepper.
Sauté aromatics: Add diced onion and cook until softened, 3–4 minutes.
Stir in garlic and cook 30 seconds, just until fragrant.
Season: Sprinkle in taco seasoning and cumin. Stir to coat the meat and onions so the spices bloom in the heat.
Add the base: Stir in beans, corn, diced tomatoes, Rotel, tomato paste (if using), and 3 cups of broth.
Simmer: Bring to a gentle simmer. Reduce heat to medium-low and cook 12–15 minutes, stirring occasionally.
Add more broth if you want a thinner soup.
Finish: Taste and adjust salt and pepper. Squeeze in lime juice for brightness. Stir in cilantro if you like.
Serve: Ladle into bowls and add your favorite toppings.
Crushed tortilla chips add great crunch.