Heat your oven to 425*F. Stir together salt and pepper in a small bowl. Put 2 tbls. of melted butter in a 10" cast iron skillet(or nonstick) with sloping sides; swirl skillet to coat sides with butter.
Working as quickly as possible to keep potatoes from darkening, arrange 2 layers of potato slices slightly overlapping in skillet, beginning at the outside edge and working inches Sprinkle with 1/4 of the salt mixture; drizzle with 2 teaspoons of the butter. Sprinkle with 1/3 cup of the cheese, being careful to keep the cheese away from the sides.
Add 2 more layers of potatoes plus another layer of the potatoes only along the outer edge to keep the top surface level. Sprinkle with 1/4 of the salt mixture. Drizzle with 2 teaspoons of the butter, then sprinkle with 1/3 cup of the cheese and the rosemary.
Repeat layering the potatoes, sprinkle with 1/4 teaspoons salt mixture and sprinkling 1/3 cup of the cheese and drizzle with remaining butter.
Heat the skillet with the potatoes over medium high heat until sizzling hot. Cook an additional 5 minutes, shaking the pan occasionally. Remove from heat; cover with foil. Lightly spray the inside surface of foil with nonstick cooking spray before covering skillet. Bake 15 minutes. Remove the foil; bake an additional 15 minutes or until the potatoes are tender. Remove from heat. Run a rubber spatula along sides of the skillet to loosen potatoes. Top skillet with a platter; iinvert the potatoes onto platter. If the potatoes stick, carefully loosen with a spatula and arrange on surface. Enjoy!
Potatoes may be made up to 4 hours ahead of serving. Invert onto baking sheet; cover and refrigerate. To serve, reheat, uncovered, at 350*F. for 25 to 30 minutes or until heated through.