Set a steamer basket in a large pot. Fill with enough water to come just below basket; bring to a boil. Add green beans to basket; reduce heat to a simmer. Cover, and cook until crisp-tender, 15 to 20 minutes.
Meanwhile, in a medium bowl, whisk together vinegar and oil; season with salt and pepper. Add green beans and sesame seeds; season with salt and pepper, and toss.
To make this recipe as prepared on "The Martha Stewart Show," cook 5 to 7 minutes.