Combine butter and flour; whisk until smooth. Add lemon zest, milk and garlic to butter mixture; whisk well. Microwave, covered, on HIGH 3-4 minutes or until thickened, stirring every 60 seconds. Add pesto; mix well.
Season chicken with rub. Grill chicken for 12-15 minutes, or until done (165 degrees).
Meanwhile, cook pasta according to package directions; drain. Set pasta aside and keep warm.
Seed and dice tomatoes. Serve chicken and sauce over pasta; garnish with tomatoes and basil.