Preheat oven to 375°.
Arrange one-third of potato slices in the bottom of a shallow 2-quart baking dish coated with cooking spray. Top with one-third of onion slices. Sprinkle with 1/2 teaspoon pepper and 1/4 teaspoon salt. Sprinkle with one-third of cheese. Repeat layers twice, ending with cheese. Dot with butter. Pour broth over potato mixture. Coat top layer with cooking spray. Cover with foil, and bake at 375° for 30 minutes. Uncover and bake an additional 30 minutes or until tender.