Preheat oven to 350℉
Peel and slice sweet potatoes into ½-inch slices and transfer to a 13x9x2-inch glass baking dish.
Blend the syrup, butter, orange juice and 2 teaspoons orange zest in a small bowl and pour over yams. Sprinkle with salt and pepper then toss to coat. Can be made 1 day ahead. Cover and refrigerate.
Sprinkle the fresh cranberries over the sweet potatoes and bake them uncovered until just tender for 45 minutes. Tent with foil after 30 minutes if sweet potatoes are getting too caramelized.
After they have baked for 45 minutes, gently stir to coat the sweet potatoes with the juices Continue baking until they are very tender and juices form a thick glaze, about 15 minutes longer. Garnish with chopped fresh parsley, if using and serve.