Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add onion and pepper; sauté 2 minutes or until crisp-tender. Add enchilada sauce; bring to a boil. Cover, reduce heat, and simmer 5 minutes.
Combine chicken, 3/4 cup of cheese, and cumin, tossing well.
Wrap tortillas in paper towels; microwave at high 30 seconds or until warm. Spoon 1/4 cup chicken mixture in center of each tortilla; roll up. Place tortillas, seam sides down, in an 11 x 7-inch baking dish coated with cooking spray. Pour sauce mixture over enchiladas; broil 3 minutes or until thoroughly heated. Sprinkle remaining 1/4 cup cheese evenly over enchiladas, and broil for 1 minute or until cheese melts. Serve with sour cream and cilantro.