Bring water to a boil in a large pot or dutch oven.
Add the dried elbow pasta and boil for 12 minutes or until cooked.
Drain water and cool the pasta thoroughly.
Combine all remaining ingredients and chill for at least 1 hour.
[Notes: I always add salt to the pot of water so that the pasta is well seasoned. The onion in the macaroni salad at L & L Hawaiian BBQ is very small, more like minced. After dicing your onion, be sure and rinse it in cold running water to remove any bitterness. I never measure out the mayonnaise, just add enough until I am satisfied. The cookbook recommends using Best Foods or Hellman's mayonnaise. I often add 2-3 Tablespoons of milk right before serving to make sure that the pasta is moist enough. The original recipe adds one small can of oil based tuna (drained), but I haven't seen it added to the salad when I have ordered it. Some reviewers are commenting that the recipe is too salty and that the salt should be reduced, so please keep that in mind. I think that I just add to taste, but the 2 teaspoons is what is in the original recipe in the cookbook.].
UPDATE May 2014: I checked with my local L&L Hawaiian BBQ and they do NOT put tuna in their macaroni salad, it is totally vegetarian.