Preheat oven to 400°F. Place potatoes on a baking sheet and bake until potatoes are pierced easily with a fork (about 40 minutes).
Mix the cinnamon and sugar together in a bowl.
Cut the potatoes in half lengthwise (if using a large potato, quarter it to portion), season with salt and pepper. Using a fork, mash the center of the potato slightly. Top with butter and sprinkle with cinnamon and sugar. Season with salt before serving.