Do not peel potatoes, cut into halves or quarters. Place in large saucepan. Cover with water. Add ½ teaspoon salt. Bring to a boil over high heat. Reduce heat to medium and boil, partially covered, until potatoes are fork tender 15 to 17 minutes. Drain potatoes. Place warm potatoes in large mixing bowl. Meanwhile, in a small bowl, whisk yogurt with mayonnaise, Dijon mustard, salt and pepper until smooth. Stir in onion and dill. Pour over warm potatoes. Mix gently serve or cover and refrigerate up to 2 days.