Boil potatoes: Cut potatoes into ½–¾-inch cubes (skins on). Boil in salted water until tender but firm, about 15 minutes. Drain well.
Cook bacon: In a Dutch oven, cook chopped bacon until crisp.Remove bacon, leaving drippings in the pan.
Sauté onions: Add sliced red onion to the drippings and cook until softened.
Make dressing: Stir in apple cider vinegar, water, sugar,celery seeds, and 1 teaspoon salt. Simmer briefly.
Combine: Add hot potatoes and reserved bacon to the dressing. Stir gently to coat evenly.
Bake: Transfer to a casserole dish or leave in the Dutch oven. Bake uncovered at 325°F (163°C) for 30 minutes if desired. Serve warm.
Notes
Sealed in an air-tight container in the fridge, hot German potato salad will stay good for up to a week.German Potato Salad is always better the second day! Prepare it ahead of time and simply reheat (or serve cold) when you're ready to serve it.