Combine rice vinegar, water, and sugar in a small saucepan.

Bring the mixture to a boil.

Add the sliced red onion to the boiling mixture.

Let the onion cool completely (about 1 hour).

Drain the pickled onion.

In a large bowl, whisk together grapeseed oil, pistachio oil, cider vinegar, and Dijon mustard.

Stir in crushed pistachios and chives.

Season the vinaigrette with salt and pepper.

Remove the skin and white pith from the grapefruit using a sharp knife.

Cut between the grapefruit membranes to release the sections into the bowl with the vinaigrette.

Add the sliced endives, parsley, tarragon, and half of the pickled onion to the bowl.

Toss the salad well to combine.

Season the salad with additional salt and pepper, if needed.

Pile the salad onto plates.

Garnish with additional crushed pistachios.

Serve the salad immediately.