1Preheat grill to 400°F.
2Lightly pound chicken breasts with a meat mallet, then score each side with a sharp knife. Coat chicken in Fajita Seasoning. Place onto hot grill, and cook 30-35 minutes, or until juices run clear, flipping after 15 minutes.
3While chicken is grilling, sauté onion and peppers in the butter over medium heat until onions are translucent. Add rice, cayenne, and pineapples. Season as desired with salt and pepper. Stir occasionally.
4When chicken is done, cut into pieces. Top taco shells with rice mixture and chicken. Serve with salsa or pico de gallo, if desired.