Combine the pasta and vegetables. Add the cooked and drained macaroni to a large mixing bowl, then add the celery, bell pepper, and green onion. Mix everything together until the vegetables are evenly distributed throughout the pasta.

Build the dressing. In a small bowl, whisk together the mayonnaise, honey mustard, sweet pickle relish, onion powder, salt, and black pepper until completely smooth, with no streaks of mayo or mustard remaining.

Dress the salad. Pour the dressing over the pasta and vegetable mixture, tossing thoroughly until every piece of macaroni is evenly coated.

Chill before serving. While the salad can technically be eaten right away, covering and refrigerating it for at least an hour is strongly worth the wait — that rest period gives the flavors time to meld and deepen, turning a good salad into a noticeably better one.