Rub fajita seasoning on all sides of chicken; cover and chill 30 minutes.
Cook chicken in a large nonstick skillet over medium-high heat, stirring constantly, 4 minutes or until done. Remove from skillet, and keep warm.
Coat skillet with cooking spray; add onion and next 3 ingredients, and saute until tender. Stir in black beans and cilantro; cook, stirring constantly, until thoroughly heated.
Coat 1 side of each tortilla with cooking spray; layer chicken, vegetable mixture, and cheese evenly on uncoated side of half of tortillas. Top with remaining tortillas, coated side up. Cook in skillet over medium heat until lightly browned, turning once. Serve immediately.