Peel and cut the potatoes into small cubes and place them in a large bowl.
Add the chopped red onion to the potatoes.
In a small bowl, whisk together the vinegar, olive oil, sugar, salt, and pepper. Pour the mixture over the potatoes and onions and mix until everything is evenly coated.
Cover the bowl with plastic wrap and let marinate in the refrigerator for at least 30 minutes.
Remove the bowl from the refrigerator and add the fresh parsley. Stir to combine.
Serve the salad at room temperature or chilled.
Interesting Facts
This recipe is traditionally served at Spanish barbecues.
The vinegar and olive oil help to give the potato salad a tangy and delicious flavor.
Fresh parsley adds a bright, herby flavor to the salad.