Preheat oven to 350 °F.
In a small saucepan over medium-low heat, melt the butter. Stir in brown sugar, granulated sugar, cinnamon, nutmeg, salt, ginger, and maple syrup. Stir and cook until the mixture is fully combined
Remove from heat. Stir in the vanilla extract and the juice of half an orange. Mix well so the citrus integrates into the glaze.
Place the sliced sweet potatoes into the prepared cast iron or 8 × 11 baking dish (a little overlap is cool). Pour the glaze over the sweet potatoes, and top with a little more brown sugar.
Cover the dish with foil and bake for ~45 minutes. At the 45-minute mark, check for doneness (pierce a slice with a fork: it should be tender but not mushy). If not yet tender, continue baking in 5-minute increments.
Once tender, remove foil. Baste the sweet potatoes with the glaze from the bottom of the dish. Bake for an additional 5–10 minutes.
Serve hot. The sauce will continue to thicken as it cools.