Preheat the oven to 425°F. Line a baking sheet with parchment paper or aluminum foil.
Using a fork, poke several holes all over each sweet potato to allow steam to escape while baking.
Brush each sweet potato with olive oil to coat the skin evenly.
Sprinkle the sweet potatoes with kosher salt, ensuring each one is seasoned all over.
Place the sweet potatoes on the prepared baking sheet, spacing them apart to allow air circulation.
Bake for 45 to 60 minutes, depending on the size of the sweet potatoes. To check for doneness, insert a fork into the thickest part; it should glide in easily with no resistance.
When the sweet potatoes are tender, remove them from the oven and let them rest for about 5 minutes to cool slightly.
Slice each sweet potato open lengthwise and gently fluff the inside with a fork.
Top with butter, salt, and pepper.
Serve immediately while hot.