To make the marinade: Use a shallow, non metal container and combine the ingredients. Add the chicken to the marinade, turning to coat each side. Cover and refrigerate for 4 hours, turning occasionally.
Remove the chicken breasts from the marinade and discard the marinade. Cook the chicken breasts over direct/medium heat. Preheat a hotplate over direct/high heat and cook the onion slices, tomato slices and capsicum
quarters. The chicken and onion will take 4 to 8 minutes each side and the tomato and capsicum will take 3 to 4 minutes each side.
Wrap the tortillas in foil and heat for about 1 minute. Cut the capsicum into strips and slice the chicken. Place the chicken, onion, tomatoes, capsicum and avocado in warm tortillas and roll up to eat. Serve with salsa.