- 1 1/2 pounds Yukon Gold potatoes (about 5 medium), unpeeled
Cook potatoes in large pot of boiling salted water until tender, about 30 minutes. Drain. Cool to just warm, 10 to 15 minutes; peel potatoes. Cut each potato in half, then cut into 1/3-inch slices.
Place warm potatoes in large bowl. Stir red wine vinegar and sugar in small bowl until sugar dissolves, then drizzle over potatoes. Toss to coat. Mix in onion slices. Season to taste with salt and pepper. Cool to room temperature.
Add olive oil and parsley to potatoes. Toss well and let marinate at least 20 minutes and up to 2 hours at room temperature.