Preheat the oven to 350°F. Spray a 9×13-inch casserole dish with non-stick cooking spray and set aside.

In a large skillet over medium-high heat, cook 1 lb ground beef and 1 medium diced yellow onion until the beef is browned and the onion is softened, breaking the meat into crumbles as it cooks.

Add 2 medium cloves garlic, minced, and sauté for 1–2 minutes more.

Stir in 1 tbsp taco seasoning and ½ cup water; cook until the seasoning is well combined with the meat.

Add 1 can (14.5 oz) fire-roasted diced tomatoes (with juices), 4 oz green chiles, 1 can (15 oz) black beans (drained and rinsed), and 1 can (15 oz) corn (drained). Stir to combine and heat through, then remove the skillet from the heat.

Assemble the lasagna in the prepared 9×13 dish: arrange 6 small corn tortillas in an even layer on the bottom, overlapping slightly to cover the base.

Spread one-third of the meat-and-vegetable mixture evenly over the tortillas, then sprinkle one-third of the 4 cups shredded jack and cheddar cheese over the meat.

Repeat two more times: a layer of 6 tortillas, one-third of the meat mixture, and one-third of the cheese, so you have three tortilla/meat/cheese layers total and all tortillas and cheese are used.

Cover the dish with aluminum foil and bake for 30 minutes, until the casserole is bubbly and the cheese is fully melted.

Remove from the oven and let the casserole sit for 10 minutes before slicing.

Garnish with 1 medium diced tomato and 1 tbsp chopped cilantro. Serve warm with sour cream and avocado on the side.