To make a basic macaroni salad, just follow these guidelines: The pasta: Cook 1 pound elbow macaroni (for really local Hawaiian style, cook until soft and fat, but you can go al dente if you prefer). The flavoring: Stir in ¼ cup very finely grated onion. Not minced, chopped or sliced—grated. It should be liquidy (this is how they do it at Diner’s, a local eatery in Kalihi). The mayo: At least 2½ cups for real local style. But there are no rules, so use less if you like. Or more. The finale…