Wash the baby potatoes thoroughly to remove any dirt. Place them in a large pot and fill with water, ensuring the potatoes are fully submerged.
Bring the pot of water to a boil. Once boiling, reduce the heat to a simmer and cook the potatoes for about 15-20 minutes, or until tender when pierced with a fork.
Drain the cooked potatoes in a colander and let them cool slightly. When cool enough to handle, cut them into quarters.
In a mixing bowl, combine the Greek yogurt, mayonnaise, Dijon mustard, apple cider vinegar, salt, and black pepper. Whisk until well combined and smooth.
Add the chopped dill, red onion, celery, and cherry tomatoes (if using) to the dressing and mix well.
Add the warm potatoes to the bowl with the dressing, gently stirring to coat the potatoes evenly without mashing them.
Cover the bowl with plastic wrap and refrigerate for at least 30 minutes before serving to allow the flavors to meld.