Cook the meat and veggies. In a large skillet or frying pan, cook the ground beef over medium heat until browned. Add the diced onion, minced garlic, and diced bell pepper. Cook until the vegetables are tender and the meat is fully cooked.
Season the cooked meat and veggies. Drain any excess grease from the skillet. Add the black beans, corn, diced tomatoes, and tomato sauce to the skillet, stirring well to combine. Season the mixture with chili powder, cumin, dried oregano, salt, and pepper. Allow the flavors to meld together over medium heat for 5-7 minutes, stirring occasionally.
Begin Layering. Grease a baking dish and layer the bottom with a thin amount of the meat and vegetable mixture. Place a tortilla shell on top to cover the mixture.
Add some cheesy goodness. Spoon a generous portion of the meat and vegetable mixture onto the tortilla shell, spreading it evenly. Sprinkle a handful of shredded cheese on top.
Finish layering. Place another tortilla shell on top and repeat the layering process until all the ingredients are used, finishing with a layer of meat and vegetables and a generous amount of shredded cheese on top.
Cover and bake. Cover the baking dish with foil and bake in the preheated oven for 20-25 minutes. Then, remove the foil and continue baking for an additional 5-10 minutes, or until the cheese is melted and bubbly.
Let the lasagna rest. Once the Mexican Lasagna with Tortilla Shells is cooked to perfection, remove it from the oven and let it cool for a few minutes. Garnish with fresh cilantro leaves for a vibrant touch.
Serve and enjoy! Slice the lasagna into portions and serve it warm.