Heat a large skillet over medium heat, then add ground beef and diced onions. Cook until meat is browned and onions are translucent, then drain excess grease and mix in seasonings with ⅔ cup water and cook until water is reduced.
Line a 9x13 baking dish with meat mixture, then top with diced green chilies, nacho cheese, and shredded cheese.
Bake for 10-15 minutes or until cheese is melted and bubbly. Layer corn chips, shredded iceberg lettuce, sour cream, and cilantro lime sauce.
Top the whole thing off with sliced cherry tomatoes, serranos, and green onions, then serve.
Notes
To get the perfect drizzle, you can use small piping bags or add sour cream and cilantro crema to ziplock bags and cut off a small portion of one corner to create a makeshift piping bag.
You can prepare this dish ahead of time, but I recommend adding the chips and toppings right before serving so they stay fresh.
If you're sharing with kids or picky eaters, you can serve the toppings in individual bowls and let everyone assemble their own portions.
Leftovers can be stored for 3-4 days in an airtight container in the refrigerator. Store chips separately, if possible, for a better texture.
The base of the casserole is freezer-safe, but I wouldn't try freezing portions that have chips or veggies on top.
You can reheat leftovers by microwaving or heating in the oven at 350°F for 20-25 minutes or until heated through (smaller portions may require less time).