Green Bean Salad with Sliced Vegetables

This recipe is adapted from one in the wonderful book by Edna Lewis, TheTaste of Country Cooking. 

1 pound green beans (your box usually contains only 1/2-pound, so you may want to reduce the recipe)
Other vegetables — sliced tomatoes if you have them, or gently steamed and sliced Tokyo Turnips
Salt
Vinaigrette Dressing:
1/4 cup vinegar
1/2 cup olive oil
1/4 teaspoon salt
1/8 teaspoon fresh-ground black pepper
2 teaspoons grated onion

Snip off the ends of the beans and drop them into a 3-quart pot of rapidly boiling water over high heat. Let the beans boil for 12 minutes, uncovered, skimming off any scum that arises. Add salt while boiling, 2 teaspoons to 1/2 gallon of water.  Drain and plunge the beans into ice water for 2 minutes. Remove the beans from the water and lay them on a clean towel to dry.  

Make a vinaigrette dressing by combining the vinaigrette ingredients. Place the beans and other vegetables (tomatoes could wait) into your salad bowl and pour the dressing over them. Leave them to marinate for 1/2 hour.