Add all dressing ingredients to mixing bowl and whisk to combine fully. Cover and refrigerate until ready to use.
Bring a large pot of salted water to a boil, then add dried pasta. Boil pasta 2 - 5 minutes longer than the package lists for al dente. Drain.
Immediately add pasta to a large mixing bowl, add vinegar and stir until pasta absorbs the vinegar. Let sit 10-15 minutes.
Add half of the dressing to the pasta, stir well. Let sit another 10-20 minutes.
Add the green onions, celery, carrots and onion. Stir, then add remaining dressing and stir again.
Cover bowl with plastic wrap and refrigerate at least 2 hours, but longer is better.
