Sprinkle taco seasoning over both sides of chicken.
Place a large nonstick skillet over medium heat until hot. Coat chicken with cooking spray.
Add chicken to pan, and cook 7 minutes on each side or until chicken is done.
Remove chicken from heat; sprinkle with cheese. Cover and let stand 3 to 4 minutes or until cheese melts. Garnish with jalapeño slices, if desired.