Preheat your oven to 350°F (175°C).
In a large skillet, cook the ground beef and chopped onion over medium heat until the beef is browned and the onion is soft, about 5-7 minutes. Drain any excess fat.
Stir in the black beans, diced tomatoes, cumin, garlic powder, salt, and pepper. Cook for an additional 3-5 minutes until heated through.
In a mixing bowl, combine 1 cup of the enchilada sauce with half of the shredded cheese.
In the prepared baking dish, spread a layer of the ground beef mixture on the bottom. Top with 4 corn tortillas, half of the cheese mixture, and another layer of the beef mixture. Repeat this process until all ingredients are used, finishing with a layer of tortillas on top.
Pour the remaining enchilada sauce over the top and sprinkle with the remaining cheese.
Cover the baking dish with aluminum foil (optional) to prevent over-browning and bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 5 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let it cool for a few minutes before serving. Garnish with fresh cilantro if desired.