Halve the red onion, peel it and cut from near the root end to the blossom end at 3/4-inch intervals leaving it intact at the root end. Turn the onion 90° and slice across the cuts so you have thin slices that are about 3/4-inch long. Add them to the bottom of a large mixing bowl, sprinkle with 1 teaspoon of the kosher salt and pour the rice vinegar over the onions. Stir well and let stand while you prepare the rest of the ingredients.

Begin by halving the grapes. If they are particularly large, you might want to quarter them. Once they are all halved or quartered, transfer them to the mixing bowl on top of the onions but do not stir yet.

Next, cut all the broccoli florets away from the stems. Reserve the stems for another use (*See Notes) and cut the florets down to bite sized. They should be roughly the same size as the pieces of grape. Scrape the broccoli into the bowl on top of the grapes, but again, do not stir yet.

Use a large hole side of a box grater (like one you would use to grate Cheddar) to grate the carrots. Add those to the bowl. Add the remaining ingredients and toss until everything is evenly combined and a thin dressing has formed from the rice vinegar and mayonnaise. If you want it creamier, add a little bit of mayonnaise at a time. Remember, though, that as the salad sits in the refrigerator, the vegetables and grapes will release some liquid and increase the amount of dressing in the container.

Transfer to a tightly lidded container and refrigerate for at least an hour before serving but preferably overnight. Toss before serving to re-distribute the dressing.

Leftovers stored in a tightly lidded container in the refrigerator will last for at least 7 days.