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

In a large mixing bowl, combine the cooled macaroni, drained tuna, diced celery, green bell pepper, red onion, and optional peas.

In a separate bowl, whisk together the mayonnaise, apple cider vinegar, Dijon mustard, salt, and black pepper. Pour the dressing over the pasta mixture and stir until well combined.

Cover the salad and refrigerate for at least 30 minutes before serving to allow the flavors to meld. Garnish with fresh parsley if desired.