German-Style Purple Potato Salad

Preheat oven to 425 degrees F.

Toss potatoes in a large bowl with oil, 1/4 teaspoon salt and pepper. Transfer to a large rimmed baking sheet. Roast, stirring once, until tender and browned, 20 to 25 minutes.

Meanwhile, cook bacon in a medium skillet over medium heat, stirring occasionally, until crisp, 5 to 7 minutes. Transfer with a slotted spoon to a paper-towel-lined plate. Add onion, vinegar and mustard to the pan. Cook, stirring constantly and scraping up the browned bits, for 1 minute. Remove from heat.

Transfer the potatoes to a large bowl and drizzle with the dressing; stir to combine. Add celery and the bacon and toss to coat. Season with the remaining 1/4 teaspoon salt and more pepper to taste.