Preheat oven to 450 degrees. Wash and dry all produce. Halve, peel, and thinly slice onion; mince a few slices until you have 2 TBSP (4 TBSP for 4 servings). Halve buns. Cut potatoes into ¼-inchthick rounds. Toss on a baking sheet with a large drizzle of oil, half the Fry Seasoning, salt, and pepper. Arrange in a single, overlapping layer. Roast on top rack until lightly browned, about 20 minutes.