Start by heating a large pot over medium heat. Add your ground beef and break it apart as it cooks. It should take about 5–7 minutes to brown evenly. Once it’s nearly done, toss in the chopped onion and minced garlic. Cook for another 2–3 minutes until the onion softens and the garlic smells amazing. If there’s extra grease, go ahead and drain it out.
Now stir in the taco seasoning. Make sure it coats the meat well—that's where all the taco flavor comes from! Then pour in the black beans, pinto beans, corn, diced tomatoes, Rotel, broth, and tomato sauce. Give it all a big stir to combine.
Turn the heat down slightly and bring your soup to a gentle simmer. Let it bubble away uncovered for 20–25 minutes. Stir it now and then to prevent sticking. As it simmers, the flavors will deepen, and the soup will thicken up beautifully.
Ladle the soup into bowls while it's hot. Now comes the fun part—top it with shredded cheese, sour cream, fresh avocado, jalapeños, or crunchy tortilla chips. Whatever you like on tacos works great here!