Heat oven to 425°F. In a medium bowl, combine black beans, corn, salsa, chicken, and cilantro.
Coat the bottom of a baking pan with vegetable cooking spray. Place 1 tortilla in coated pan. Top with 1-1/2 cups of the bean mixture and 1/4 of cheese. Layer 3 more times, finishing with the last tortilla.
Bake in the oven 15 to 20 minutes, or until cheese melts and filling is hot. Serve with sour cream, if desired.