Preheat oven to 350°F. Grease a 9x13 baking dish (I use butter). Add sweet potatoes, sugar, and rum, and toss to coat.
Toss every 30 minutes, baking until potatoes are tender, about 60-90 minutes.
Remove from oven, stir in butter, salt, and pepper before serving.
Notes
*Melting butter may make it easier to toss.Keep leftovers in an airtight container in the fridge for up to 5 days. Add to oven after turkey has roasted for one hour.