Begin by filling a large pot with water. Add a tablespoon of kosher salt and bring it to a rolling boil. Carefully toss in the halved baby red potatoes. Allow them to cook until tender, which should take about 15-20 minutes. Keep an eye on the potatoes; you're looking for a fork to easily pierce them but not break apart.

While the potatoes are cooking, mix up your dressing. In a medium bowl, combine the reduced-fat mayonnaise, Dijon mustard, light sour cream, and garlic salt. Whisk until smooth. Stir in the freshly chopped dill and season with black pepper, adjusting to your taste.

Once the potatoes reach that perfect tenderness, drain them in a colander. Give them a few moments to cool off and dry out; this will help avoid a watery salad.

In a large mixing bowl, combine the cooled potatoes and chopped red onion. Drizzle the dressing over them and gently stir to coat all the potato pieces evenly.

Finally, add the distilled white vinegar and stir again. Give it a taste and adjust seasoning, if necessary. If you'd like, this is a great time to sprinkle in a little extra dill for garnish.

Cover the bowl with cling film or a lid and place it in the refrigerator for at least an hour. This chilling time allows the flavors to meld beautifully.