Slice onion and let sit for 5-10 minutes to bring out its health-promoting properties. Bring water to a boil in a steamer with a tight fitting lid. Cut ends off beans and slice fennel and onion. Steam beans and onion together for about 3 minutes, and add the fennel. Steam for another 2 minutes. Drain well and pat with paper towel so any excess water does not dilute taste. Toss with rest of ingredients. Makes 2 servings.