Brown ground beef and chopped onions in large skillet; brown 10 to 12 minutes or until thoroughly cooked, stirring constantly.
Drain well and rinse with warm water to remove all fat; return beef/onions to skillet.
Add corn, black beans, tomatoes, chilies/jalapenos, and taco seasoning mix; mix well. Reduce heat; simmer 5 minutes.
Meanwhile, spray 12×8-inch (2-quart) baking dish with nonstick cooking spray. Cut each tortilla in half; place 8 halves in the bottom of the sprayed baking dish, overlapping slightly.
Spoon half of the beef mixture evenly over tortillas. Spoon sour cream over beef mixture; spread evenly. Top with the remaining 8 tortilla halves and the remaining beef mixture. (Cover tightly with foil & Freeze for later OR cook as directed below…).
(Thaw overnight if frozen) Heat oven to 350ºF. Bake at 350ºF for 25 minutes. Remove from oven; sprinkle with cheese. Cover; let stand 5 minutes or until cheese is melted. Sprinkle with chopped cilantro and serve with fresh chopped lettuce, tomatoes, salsa, black olives, etc… /.