
Cook the pasta: In at least 2 quarts of salted water (1 ½ teaspoons of salt per quart of water), cook the pasta according to package directions until al dente—still slightly firm. Remove from heat, drain and rinse with cool water until the pasta reaches room temperature.
Soak the onions: While macaroni is cooking, put the chopped onions into a small bowl and sprinkle the lemon juice or vinegar, and a little water over them. This will take the edge off the onions.
Assemble the macaroni salad: Combine cooked macaroni, onions, and all other ingredients in a large serving bowl. Adjust seasonings to taste.