Place the green beans in a medium saucepan and cover with water. Bring to a boil, then cook until crisp-tender, 2 to 4 minutes. Drain the green beans and rinse with cool water to stop the cooking.
In a jar or bowl, blend the dressing ingredients together. Shake or stir before using.
Transfer to the cooled green beans to a large bowl. Add the tomatoes, red onion, and dressing. Toss to coat.
Notes
Choose fresh, firm green beans for the best texture. Blanching gives them a crisp-tender texture while preserving their bright green color.Use tomatoes that are ripe but still slightly firm. If you want to bring out more of their natural sweetness, sprinkle them with a little bit of sugar before adding them to the dish.Don't skimp on the feta cheese. It adds a nice creamy texture and salty flavor that really completes this dish.Add fresh garlic to the dressing for a more aromatic flavor.Top each serving with freshly cracked black pepper and extra virgin olive oil. The topping will give the salad an extra boost of flavor.