1 tablespoon white wine vinegar
1/2 teaspoon Dijon mustard
1/4 teaspoon salt
1/8 teaspoon freshly ground black pepper
2 garlic cloves, crushed and minced
1 tablespoon extravirgin olive oil
1/2 cup seeded chopped tomato
2 teaspoons chopped fresh thyme
1 pound green beans, trimmed
Combine first 5 ingredients in a medium bowl; slowly add oil, whisking to combine.
Stir in tomato and thyme; let stand 10 minutes.
Steam beans, covered, 7 minutes or until crisp-tender.
Cut into 2-inch pieces; add to tomato mixture, tossing gently to coat.