To prepare chicken, combine first 4 ingredients in a large bowl; toss and let stand 3 minutes. Remove chicken from marinade; discard marinade. Sprinkle chicken evenly with 1/4 teaspoon salt. Heat a grill pan over medium-high heat. Coat pan with cooking spray. Add chicken to pan; cook 6 minutes on each side or until done.
Alternatively, you can bake the chicken at 350 degrees until done. Thicker chicken breasts will take 30-45 minutes. Thinner chicken breats will be 25 minutes or so.
To prepare salsa, combine tomato and next 4 ingredients (through pepper) in a medium bowl. Add avocado; stir gently to combine. Serve salsa over chicken.