Bring a large pot of salted water to a boil over high heat, and set a bowl of ice water nearby.
Drop the green beans into the boiling water and cook for two minutes.
Remove the beans with a slotted spoon and immediately immerse them in the ice water bath.
Leave them in the ice bath for two minutes, then remove them to a kitchen towel to dry completely.
In a serving bowl, toss together the beans, tomato, and onion.
In a small bowl or jar, mix together all of the dressing ingredients and shake or whisk them until completely integrated.
Pour half of the dressing over the vegetables and toss to coat.
Top the vegetables with crumbly cheese and nuts, then finish with the remaining dressing and serve.
Refrigerate any remaining salad in a sealed container for up to five days.