Preheat oven to 425°F and line a baking sheet with parchment paper.
Wash the sweet potatoes well, dry and use a fork to poke holes all over the sweet potatoes.
Place sweet potatoes on prepared baking sheet and bake until tender through to the center, 40-50 minutes. It should be puffed up and soft when pierced with a knife.
Allow the sweet potatoes to cool, then cut the tops open with a knife and serve with a pat of butter, salt and pepper, if desired.
Notes
Storage: Cooked baked sweet potatoes will keep well for 4 to 5 days in the fridge and can be reheated in the oven or microwave. To freeze, wrap each potato in foil, then place in a freezer safe bag. They will keep for about 3 months in the freezer and you can reheat in a moderate oven.