1-1/2 pounds fresh green beans, trimmed
2 tablespoons red wine vinegar
2 tablespoons olive oil
2 teaspoons Dijon mustard
1/2 teaspoon salt
1/4 teaspoon pepper
1 cup grape tomatoes, halved
2 tablespoons grated parmesan cheese
place beans in a large saucepan and cover with water. Bring to a boil. Cook, uncovered for 8-10 minutes or until crisp-tender.
Meanwhile, for dressing, whisk the vinegar, oil, mustard, salt, and pepper in a small bowl. Drain beans; place in a large bowl. Add tomatoes and onion. Drizzle with dressing and toss to coat. Sprinkle with cheese.
I suggest letting the sauce sit on the beans for a bit so they can absorb some of the flavor. I noticed when I made it the onions tasted a lot like the sauce because they had sat in it for longer.