Bring a pot of water to a boil, then add peeled, cubed Yukon gold potatoes and boil until fork-tender, about 15 minutes (you should easily pierce cubes with a fork). Drain the potatoes and let them cool until no longer steaming, about 10 minutes, so the dressing won’t get runny.

In a large bowl, combine the cooled potatoes with chopped hard-boiled eggs, finely diced celery, finely diced onion, and sweet pickle relish until evenly distributed (visible egg pieces should be scattered throughout).

In a separate bowl, whisk mayonnaise, yellow mustard, apple cider vinegar, sugar, celery seed, salt, and pepper until smooth and thick (the mixture should look glossy).

Pour the dressing over the potato mixture and fold gently until every bite is coated without mashing the potatoes (you should still see potato cubes and egg pieces).

Refrigerate the salad for at least 3 hours or overnight to let flavors meld and the texture set, then chill until cold in the center.

Before serving, sprinkle paprika over the top for garnish and color (the surface should look lightly speckled).