Place the potatoes with skin on in a large pot of water with two tablespoon of salt and bring it to boil. Then simmer for 15 minutes. Once the potatoes are tender enough to be pierced with a knife, drain them in a colander.Place the potatoes back in the pot, and cover with a clean dry kitchen towel. Allow the potatoes to steam for 15 to 20 minutes.
As the potatoes steam, in a small bowl, whisk together the mayonnaise, buttermilk, Dijon mustard, whole grain mustard, dill, 1 teaspoon of salt, and 1 teaspoon of pepper. Set aside.
When the potatoes are cool enough to handle, cut them in quarters or in half, depending on their size. Place the cut potatoes in a large bowl. While the potatoes are still warm, pour enough dressing over them to moisten. Add the celery and red onion, 2 teaspoons of salt and 1 teaspoon of pepper. Toss well, cover, and refrigerate for a few hours to allow the flavors to blend. Serve cold or at room temperature.
Recipe by The Lady 8 Home at https://www.thelady8home.com/potato-salad-inafridays/