Cook pasta in a large pot of boiling water, according to package instructions, until “al dente” (tender but still firm to the bite). Drain.
Drain and rinse under cold water and drain again. Let it cool for 5 minutes.
In a food processor or blender, pulse all the dressing ingredients 3 or 4 times until the basil is broken down, releasing its wonderful oil into the dressing! Do not liquefy because you want to be able to see the basil and have its texture in the dressing. You will be surprised how quickly we can get the dressing infused with basil in such a short time. The basil flavor will be more intense than if you chop it up and add it to the salad.
In a large bowl, add the red onions, cover with the dressing and let it rest for 5 minutes. Add the remaining ingredients and toss to combine.