This is a Mary McDougall recipe from the Feburary 2006 McDougall Newsletter. I’ve gotten consistently good results cooking yams and sweet potatoes with these directions.
Garnet Yams (reddish skins and a deep orange flesh)
Preheat oven to 350 degrees.
Scrub the yams and cut into quarters.
Place in a single layer in a dry baking dish, skin side down. Cover with parchment paper, then cover the baking dish with aluminum foil, crimping it over the sides to hold in the steam. Bake for 1 hour, 10 minutes.