Preheat and prep: Heat the oven to 375°F (190°C). Grease a 9x13-inch baking dish.
Cut tortillas into 1–2 inch strips for easy layering and scooping.
Cook the beef: Warm oil in a large skillet over medium-high heat. Add diced onion and cook 3 minutes until softened. Add ground beef, season with a pinch of salt and pepper, and cook, breaking it up, until browned and no longer pink.
Add flavor: Stir in garlic and cook 30 seconds.
Sprinkle in taco seasoning and mix well. Add tomato sauce and diced green chiles. Simmer 2–3 minutes until slightly thickened.
Stir in beans and corn: Fold in black beans and corn.
Taste and adjust seasoning with salt, pepper, or a dash of hot sauce. The mixture should be saucy but not soupy.
Build the first layer: Scatter a layer of tortilla strips in the baking dish. Spoon half of the beef mixture over the tortillas and spread evenly.
Sprinkle about 1 cup of shredded cheese on top.
Add creamy layer (optional): Dollop and gently spread sour cream or Greek yogurt over the cheese for a richer, tangy bite.
Second layer: Add another layer of tortilla strips, then the remaining beef mixture. Top with the remaining cheese (about 2 cups) for that irresistible cheesy crust.
Bake: Cover loosely with foil and bake for 15 minutes. Remove foil and bake another 10–12 minutes until the cheese is melted, bubbly, and lightly golden.
Rest and garnish: Let the bake sit 5–10 minutes to set for cleaner slices.
Top with cilantro, green onions, tomatoes, and any favorites. Serve with lime wedges.
Serve: Scoop into bowls or cut into squares. Add shredded lettuce, avocado, and a spoonful of salsa or hot sauce on each serving if you like.