Place potatoes in a large pot and cover with cold water; add a pinch of salt. Bring to a boil, then lower to a steady simmer. Cook until a knife slides easily through the potatoes, about 18–22 minutes.

Transfer potatoes to an ice bath to cool quickly and stop cooking; this keeps them from turning mushy.

Once cool, peel the potatoes and dice into large, bite-size chunks.

Whisk together mayonnaise, mustard, apple cider vinegar, sugar, and onion powder in a small bowl until smooth and slightly glossy.

Pour the dressing over the warm (not hot) potatoes and gently toss to coat.

Stir in pickle relish, chopped celery, chopped onion, and the chopped hard-boiled eggs until evenly combined.

Taste and add a little salt if needed.

Chill for at least 1 hour to let flavors marry, or serve right away if you’re in a hurry.