1. In a medium skillet heat oil over medium-high heat. Add chicken and tomatoes; cook and stir 3 to 4 minutes or until tomatoes begin to soften. Stir in 1/4 cup of the pesto; toss to coat. Remove pan from heat; set aside.
2. Meanwhile, in a large pot cook spaghetti al dente according to package directions. Reserve 1/2 cup of the pasta water. Drain pasta; return to pot. (If pasta appears dry, gradually add reserved water and toss to coat until moist.) Add remaining pesto; toss to coat. Transfer to a serving bowl.
3. Top pasta with chicken mixture, and (if desired) serve with grated Parmesan.

Per serving: 620 calories, 30g fat, 7g saturated fat, 85mg cholesterol, 430mg sodium, 48g carbohydrate, 8g fiber, 43g protein