Heat oven to 400 F.
In large bowl, mix grapefruit juice, oil, garlic powder, cumin, paprika and red pepper until combined. Add chicken to bowl and turn to coat. Refrigerate 30 minutes or longer.
To make salsa fresca: In medium bowl, mix grapefruit segments, jicama, red onion, grapefruit juice, olive oil, cilantro and jalapeno pepper until combined. Refrigerate until ready to serve.
Remove chicken from marinade. Place chicken in baking dish. Bake 25-30 minutes until chicken is cooked through.
Serve chicken with salsa fresca.