Step 1: Cook the Macaroni: Bring a large pot of salted water to a boil. Add the elbow macaroni and cook according to package directions until al dente, usually around 7-8 minutes. Avoid overcooking the macaroni, as it will become mushy.
Step 2: Drain and Rinse: Once the macaroni is cooked, drain it immediately and rinse it thoroughly with cold water. This stops the cooking process and removes excess starch, preventing the salad from becoming sticky. Ensure all water is drained.
Step 3: Prepare the Dressing: In a large bowl, whisk together the mayonnaise, milk, apple cider vinegar, sugar, salt, and pepper until smooth and well combined. Adjust the amount of sugar and vinegar to taste, depending on the desired level of sweetness and tanginess.
Step 4: Combine Ingredients: Add the drained macaroni to the bowl with the dressing. Gently fold until the macaroni is evenly coated. If using, add the chopped onion and celery, and fold to incorporate.
Step 5: Chill and Serve: Cover the bowl with plastic wrap and refrigerate for at least 2 hours, or preferably overnight. This allows the flavors to meld and the salad to chill completely. Before serving, stir well and add more milk if needed to adjust the consistency.
Optional tips: For a richer flavor, use whole milk or add a tablespoon of sour cream to the dressing. For a tangier salad, increase the amount of apple cider vinegar. Some variations include adding grated carrots or shredded ham.