Preheat oven to 350°.
Layer about one-third of the potato slices into a well-greased 9 x 1 1/2 inch pie plate and sprinkle with half the onion.
Dot with butter and season lightly.
Repeat, ending with a layer of potatoes, butter, and seasonings.
Cover with foil and bake 1 hour.
Remove foil, test for doneness.
Bake up to 30 minutes longer or until lightly browned andtender.