Warm the pan. Heat a large nonstick or cast-iron skillet over medium heat.
Add the oil and let it shimmer.
Sauté the veggies. Add the onion and bell pepper with a pinch of salt. Cook 4–5 minutes, stirring, until softened. Add the garlic and cook 30 seconds, until fragrant.
Brown the beef. Scoot the veggies to the edges.
Add the ground beef to the center. Season with salt, pepper, cumin, chili powder, and smoked paprika. Cook, breaking it up, until browned and no longer pink, 4–6 minutes.
If excess grease remains, blot with a paper towel or drain lightly.
Build the skillet. Stir in the enchilada sauce, black beans, corn, and green chiles (if using). Bring to a gentle simmer.
Add tortilla strips. Fold in the tortilla pieces so they soak in the sauce. Simmer 3–5 minutes, stirring occasionally, until the tortillas soften and the mixture thickens slightly.
Cheese time. Sprinkle cheese evenly over the top.
Reduce heat to low, cover, and cook 2–3 minutes until the cheese melts. If you don’t have a lid, tent with foil or let it melt uncovered for a minute longer.
Finish and serve. Top with cilantro and green onions. Serve hot with lime wedges and your choice of avocado and a spoonful of Greek yogurt or light sour cream.