For dressing, whisk 1/2 cup of oil, vinegar, garlic and sugar in a medium bowl to blend. Whisk in onion, tomatoes, and 1/4 cup of basil. Season with salt and pepper. Heat remaining 1 tbs of olive oil in heavy skillet over medium high heat. Sprinkle chicken on all sides with salt and pepper as desired. Add chicken to skillet, saute until brown. Add broth, 1/2 cup of dressing and 1/4 cup of basil and bring to boil. reduce heat to medium low; simmer uncovered until chicken is cooked through. Remove from heat. Thinly slice chicken.
Divide cooked pasta over 4 plates. Top with 1 sliced chicken breast, spoon pan juices over. Garnish with remaining 1/4 cup of basil. Use remaining dressing as necessary.