In a skillet over medium heat, cook the ground beef until browned. Drain excess fat.

Add black beans, corn, and taco seasoning to the skillet. Stir to combine and cook for 5 minutes.

Preheat the oven to 350°F (175°C).

Spread a thin layer of diced tomatoes on the bottom of a 9x13 inch baking dish.

Layer 4 tortillas over the sauce, followed by half of the meat mixture, half of the sour cream, and half of the cheese.

Repeat the layers, finishing with tortillas, remaining diced tomatoes, and cheese on top.

Cover the dish with aluminum foil and bake for 20 minutes.

Remove the foil and bake for an additional 10 minutes, or until the cheese is bubbly and golden.

Let the lasagna cool for a few minutes before slicing. Garnish with cilantro and serve with avocado slices.