Boil a large pot of salted water and cook the elbow macaroni according to package instructions until al dente. Drain and rinse under cold water to cool down.

In a large bowl, combine the mayonnaise, sour cream, Dijon mustard, pickle juice, salt, and pepper. Whisk until smooth and creamy.

Add the cooled macaroni, chopped dill pickles, and diced red onion to the dressing. Stir gently until everything is well coated.

Cover the bowl and refrigerate for at least 1 hour to allow the flavors to meld. Before serving, give it a gentle stir and season more if needed. Garnish with extra dill pickles or fresh dill if desired.