Sweet Potatoes and Apple Casserole

4 small sweet potatoes (about 1 1/2 lbs.)
2 cooking apples sliced, cored, and peeled (about 1 lb.)
3 Tbsp. sugar
1/2 tsp. ground cinnamon
dash of white pepper
2 tsp. melted butter

Spray baking dish with cooking spray. Layer half of each of the sweet potatoes and apples, in an 8 inch square baking dish. Combine sugar, cinnamon, white pepper; sprinkle half of mixture over potatoes and apples. Drizzle with half of margarine. Repeat, procedure with remaining ingredients. Cover casserole and bake at 350 degrees for 1 hour.