In a small mixing bowl, WHISK together the 7 dressing ingredients; SET aside.
BRING a large pot of salted water to a BOIL over medium-high heat; ADD uncooked pasta; COOK 5 minutes.
ADD green beans; COOK until beans are tender and the pasta is tender but firm, about 5 to 6 more minutes.
DRAIN; RINSE with cold water; TRANSFER to a large serving bowl.
ADD tomatoes and onion; POUR salad dressing over top; TOSS to coat.
Serve immediately, or cover and chill up to 2 hours.
Per Serving (excluding unknown items): 332 Calories; 19g Fat (49.9% calories from fat); 5g Protein; 37g Carbohydrate; 1g Dietary Fiber; 0mg Cholesterol; 183mg Sodium. Exchanges: 2 Grain(Starch); 1/2 Vegetable; 0 Fruit; 3 1/2 Fat; 1/2 Other Carbohydrates.