Potato Salad (Kompir Salata)

4 large potatoes, boiled, peeled, and cut into thin cross-sectional circles
1 medium onion (minced)
1 1/2 tablespoon white vinegar
3 tablespoons sunflower oil
Salt and freshly ground black pepper to taste

1. Place potatoes in a large bowl.
2. In a screw-top jar, add remainder of ingredients, cover with the lid, shake vigorously, and pour dressing over potatoes.
3. Refrigerate overnight or at least a few hours, before serving