Preheat the oven to 400°F.

In a large oven-safe skillet over medium-high heat, cook the ground beef and diced onion until the beef is browned and the onion is softened, about 6 to 8 minutes. Drain excess grease if needed.

Stir in the garlic and taco seasoning, then add 1/2 cup of the enchilada sauce, the black beans, and the corn. Cook for 1 to 2 minutes until heated through.

Add the tortilla strips and gently fold them into the beef mixture until evenly coated.

Pour the remaining enchilada sauce over the top and sprinkle with 1 1/2 cups of the shredded cheese.

Transfer the skillet to the oven and bake for 10 to 12 minutes, until the cheese is melted and bubbly.

Remove from the oven, top with the remaining 1/2 cup cheese if desired, and let rest for 5 minutes. Garnish with cilantro and serve warm with sour cream if using.