No longer just picnic fare, this Red Potato and Dill Salad is a goes-with-everything summer side. This simple recipe combines boiled red potatoes with a flavorful dressing of sharp dijon and whole grain mustard, creamy mayonnaise and tart buttermilk. Throw in some chopped red onion and celery for crunch and color, salt and pepper, lots of fresh dill and you have an incredibly…