Preheat your oven to 350°F (175°C).
In a large skillet, cook the ground beef over medium heat until browned, breaking it apart as it cooks.
Add the chopped onion and minced garlic to the skillet, cooking until the onion is translucent.
Stir in the black beans, corn, diced tomatoes, chili powder, and cumin. Cook for another 5 minutes.
In a 9x13 inch baking dish, spread a layer of the beef mixture at the bottom.
Place a layer of corn tortilla strips over the beef mixture, followed by a layer of shredded cheese.
Repeat the layers, alternating between the beef mixture, tortillas, and cheese until all ingredients are used, finishing with a cheese layer on top.
Cover the baking dish with aluminum foil and bake in the preheated oven for 30 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Once baked, remove from the oven and let cool for 10 minutes before serving.
Serve with sour cream and garnish with fresh cilantro, if desired.