Preheat oven to 400ºF and line a baking sheet with parchment paper or foil (for easy clean-up).
Rub oil over each sweet potato half, including the cut side.
Place the halves cut-side down on the baking sheet, with at an inch in between.
Bake in the oven according to the time chart in the notes below. The sweet potatoes are done when a fork easily pierces the potato. To double-check doneness, turn one over and confirm that the inside flesh is nice and tender. You'll be able to easily leave imprints with the tines of a fork.
Remove from oven and carefully flip over.
Season with salt and pepper.
Notes
Baking time guidelines for sweet potatoes:Small: 25 minutes, Medium: 30 minutes, Large: 35-40 minutesWhen in doubt, start checking for doneness at the shortest time.Note that you can bake as many sweet potatoes as will fit on your baking sheet. Whether you bake one or six, the time is the same.