Easy and pleasant. Please do not top with marshmallows, as that is an abomination.
Preheat the oven to 400. Grease a baking dish.
Combine the sugar, cinnamon, salt, and nutmeg. Add the melted butter and stir to make a paste.
If you're using canned sweet potatoes, drain them. Spread the potatoes in the dish and distribute the butter-sugar mixture evenly over them. Use a spoon or spatula to toss the potatoes so they are coated with the mixture.
Cook for 30-40 minutes. If you're using fresh potatoes, stir every 15 minutes to keep the sauce distributed well. If you're using canned, let it be, so they don't turn into mush.