• Step 1: Bring a large pot of salted water to a boil. Add the elbow macaroni and cook according to package instructions, about 7-9 minutes, until al dente. Drain the macaroni and rinse with cold water to stop the cooking process.
• Step 2: In a large mixing bowl, combine the mayonnaise, sour cream, pineapple juice, white vinegar, sugar, salt, and black pepper. Whisk until the dressing is smooth and creamy.
• Step 3: Add the cooked and cooled macaroni, diced carrot, diced celery, sliced green onions, and diced pineapple (if using) to the dressing. Gently stir until the ingredients are evenly coated.
• Step 4: Cover the bowl and refrigerate the Hawaiian macaroni salad for at least 2 hours, or up to 3 days, to allow the flavors to meld together.
• Step 5: Before serving, give the salad a gentle stir to redistribute the dressing. Taste and adjust seasoning if necessary.