1. For the chicken marinade, pour the grapefruit juice, oil, garlic powder, cumin, paprika, and cayenne pepper into a small bowl and mix well.
2. Place the chicken in a large resealable plastic bag or glass dish.
3. Add the marinade and mix to coat the chicken pieces well.
4. Refrigerate for 30 minutes or longer to allow the flavors to develop further.
5. Meanwhile, make the salsa by mixing all the ingredients in a small bowl and cover.
6. Refrigerate until ready to serve.
7. Drain the chicken, discard the remaining marinade.
8. Grill the chicken over medium-high heat for 6 to 8 minutes on each side or bake it for 15 to 20 minutes in a preheated oven at 200°C (Th. 6/7).
9. Serve it accompanied by the Fresh Salsa.