Brown the beef: Heat a skillet over medium-high.
Add ground beef, season lightly with salt and pepper, and cook until browned, breaking it up with a spoon. If the meat is very lean, add a little olive oil to prevent sticking.
Add onion and garlic: Stir in the diced onion and cook 3–4 minutes, until softened. Add the minced garlic and cook 30–60 seconds, just until fragrant.
Season: Sprinkle in the taco seasoning and cumin.
Toss to coat the beef and onions so the spices bloom and become aromatic.
Transfer to the slow cooker: Move the beef mixture into your crockpot. Add the diced tomatoes, tomatoes with green chiles, black beans, pinto beans, corn, broth, and tomato paste. Stir well to combine.
Cook low and slow: Cover and cook on Low for 6–8 hours or on High for 3–4 hours.
The longer cook on Low yields a deeper, cozier flavor.
Taste and adjust: Before serving, taste and adjust salt and pepper. If you want more heat, add a pinch of cayenne or a few dashes of hot sauce.
Serve with toppings: Ladle into bowls and finish with cheese, a dollop of sour cream, cilantro, avocado, and a squeeze of lime. Add tortilla chips for crunch.