In a large bowl, mix together mayonnaise, yogurt, dijon mustard, garlic salt, olive oil, vinegar, and pepper until completely combined to make a dressing.
In a large pot, place potato wedges and cover with water. Cook over medium-high heat until tender (about 10-15 minutes depending on the size of the chunks).
Once potatoes are tender, drain and add to the large bowl of dressing. Toss to coat.
Mix in sweet onion and dill. You can serve it warm, or refrigerate for 2-3 hours and serve cold.
Notes
The key to cooking perfect potatoes for red potato salad: simmer them instead of a hard boil. You want your potatoes to be soft and creamy and so that when you pierce them with a fork, they are tender.Depending on the size that you cut your potatoes into (and make sure that they are cut into evenly-sized pieces), the potatoes should cook in 8-12 minutes.