Bring a large pot of salted water to a boil. Add green beans and cook for 2 minutes. Drain and pat dry.

In a mixing bowl, combine cooked green beans, halved grape tomatoes, sliced Vidalia onion, and crumbled feta. Gently stir.

In a small bowl, whisk together lemon juice, olive oil, mustard, minced garlic, salt, and pepper. Emulsify well.

Drizzle dressing over salad. Gently toss to coat ingredients without breaking feta.

Let the tossed salad rest for 15 minutes at room temperature.

Toss once more before serving, optionally garnishing with extra feta or fresh herbs.