Start by filling a large pot with water and adding a generous pinch of salt. Bring to a boil over medium-high heat.

Add the potatoes and cook for 15-20 minutes until fork-tender. Drain, cool slightly, peel, and cube.

In a mixing bowl, combine mayonnaise, Dijon mustard, Cajun seasoning, salt, and pepper. Whisk until smooth.

Fold in the cooled potato cubes, diced celery, onion, and chopped bell pepper. Mix gently.

Cover and refrigerate for at least 1 hour, preferably overnight to enhance flavors.

Before serving, give the salad a gentle stir and garnish with chopped green onions.