Preheat the oven to 350°F (175°C).
Cut each small flour tortilla in half and set aside.
In a large bowl, combine the cooked shredded chicken, sour cream, black beans (drained), 1½ cups of the enchilada sauce, drained corn, garlic powder, ground cumin, chili powder, half of the chopped cilantro, and the salt. Mix until evenly combined.
Spoon about one third of the chicken mixture into the bottom of a 9×13 baking dish and spread into an even layer.
Place one layer of the halved tortillas over the chicken mixture, then sprinkle one third of the shredded cheese over the tortillas.
Repeat the layers two more times: one third of the chicken mixture, a tortilla layer, and one third of the cheese. For the final (third) layer, pour the remaining enchilada sauce over the top tortillas and finish with the remaining shredded cheese.
Bake uncovered for 22–25 minutes, or until the cheese is melted and bubbly and the casserole is heated through.
Let the lasagna rest a few minutes, then sprinkle with the remaining chopped cilantro and serve with extra sour cream, chopped tomatoes, or additional cilantro if desired.
