
Bring a large pot of well-salted water to a boil. Add the elbow macaroni and cook until softer than al dente, about 1 to 2 minutes longer than the package suggests. Drain thoroughly, then transfer the warm pasta to a large bowl and toss with the vinegar. Let it stand for about 10 minutes so the macaroni can absorb the tangy flavor.


In a separate bowl, whisk the mayonnaise, milk, sugar, salt, and black pepper until smooth. Add the dressing to the cooled macaroni along with the grated carrots and finely grated onion, if using. Fold until every piece is evenly coated, adding a little more milk if the salad feels too thick. Cover and refrigerate for at least 2 hours, preferably overnight. Stir before serving and adjust seasoning if needed.







