1. Drain salsa in a colander over a bowl, reserving liquid. Set salsa aside.
2. Combine reserved liquid, oil, salt, and pepper in a large zip-top plastic bag. Add chicken and tomato to bag; seal and shake gently to coat. Chill 30 minutes.
3. Prepare grill.
4. Remove chicken and tomato from bag, reserving marinade. Place chicken on grill rack coated with cooking spray; pour reserved marinade over chicken. Place tomato slices on grill rack. Grill chicken 6 minutes on each side or until done. Grill tomatoes 5 minutes on each side or until lightly browned. Serve chicken with tomatoes; top with reserved salsa and queso fresco.