Preheat oven to 350 degrees F. Coat a 9-inch deep-dish pie plate with cooking spray. In a large bowl, combine yams, egg whites, 1/4 cup brown sugar, and the cinnamon; mash until well combined. Spoon half the mixture into pie plate, spreading it evenly over bottom and up sides of pie plate to create a crust.
Pour cherry pie filling into crust then cover with remaining yam mixture. In a small bowl,combine pecans,the remaining brown sugar,and melted butter. Mix well and sprinkle over top. Bake 55 to 60 minutes,or until set and top is golden. Allow to cool slightly before serving.