Cook the Potatoes: Wash the red potatoes thoroughly and place them in a large pot with water and a pinch of salt. Bring to a boil, then simmer until fork-tender, about 30 minutes. Drain and let steam covered for 10 minutes.

Prepare the Eggs: Place the eggs in a saucepan, cover with cold water, and bring to a boil. Remove from heat, cover, and let sit for 10 minutes. Cool under running water, peel, and chop.

Make the Dressing: In a mixing bowl, combine mayonnaise, buttermilk, Dijon mustard, dried dill, salt, and pepper. Whisk until smooth.

Prep the Vegetables: Peel half the skins from the cooked potatoes, then dice. Chop cucumber, onion, and celery into small cubes.

Combine Ingredients: Add chopped eggs, potatoes, and veggies to a large bowl. Pour dressing over and gently fold to mix.

Chill and Serve: Cover and refrigerate for at least 2 hours, preferably overnight, before serving.