Preheat the oven to 350 degrees and grease an 11-inch by 7-inch baking dish with nonstick cooking spray.
Peel and slice the sweet potatoes into 1/4-inch thick slices.
Place the sweet potatoes into a baking dish and line them up.
Pour the melted butter and maple syrup over the potatoes.
Cover the baking dish with aluminum foil and bake for 30 minutes.
Just before the potatoes come out of the oven, mix the brown sugar, cinnamon, nutmeg, ginger, and pecans in a bowl.
Remove the sweet potatoes from the oven and take off the aluminum foil.
Sprinkle the brown sugar mixture over the sweet potatoes and return them to the oven, uncovered.
Bake another 30 minutes and serve.