Warm the skillet: Place a large, deep skillet over medium-high heat. If your beef is very lean, add a drizzle of olive oil.
Brown the beef: Add the ground beef and cook, breaking it up with a spoon, until no longer pink.
Season lightly with salt and pepper. Spoon off excess fat if needed to avoid a greasy sauce.
Add aromatics: Stir in the diced onion and bell pepper. Cook 3–4 minutes until softened.
Add the garlic and cook 30 seconds, just until fragrant.
Season it up: Sprinkle in the taco seasoning and cumin. Stir to coat the beef and veggies so the spices bloom and become fragrant.
Build the base: Pour in the diced tomatoes with green chiles, tomato sauce, and beef broth. Stir to combine and bring to a gentle simmer.
Beans and tortillas: Fold in the black beans and pinto beans.
Add the tortilla strips and stir so they soak up the sauce. Tip: Reserve a handful of strips to scatter on top for extra texture.
Simmer briefly: Reduce heat to medium and let everything bubble for 3–5 minutes, stirring occasionally. You want the tortillas to soften and the liquid to thicken into a saucy, scoopable mixture.
Cheese time: Sprinkle 1 1/2 cups of cheese evenly over the skillet. Cover with a lid (or tent with foil) and cook 2–3 minutes until the cheese melts.
Uncover, scatter remaining tortilla strips, and top with the last 1/2 cup cheese for a melty-meets-crispy finish.
Taste and adjust: Give it a taste and adjust salt, pepper, or heat with hot sauce if you like. The sauce should be cozy and well-seasoned, not watery.
Finish with toppings: Off the heat, add fresh touches: sour cream, green onions, cilantro, avocado, jalapeños, and a squeeze of lime. Serve straight from the skillet with extra tortillas or chips on the side.