Preheat oven to 375°F.
In a small bowl, combine cinnamon, brown sugar, apple cider vinegar, and salt.
Pour melted butter, maple syrup, and orange juice over the sugar mixture and mix well.
Place sweet potato chunks in a large, deep baking dish (at least 9x13") and pour the sugar butter mixture over them. Stir to coat evenly.
Cover the dish and bake for 20 minutes.
Prepare the streusel topping: mix oats, flour, pecans, brown sugar, cinnamon, salt, and pumpkin pie spice. Add the cold, cubed butter to the bowl and mix together with your fingertips until combined. Chill in the fridge to firm up slightly.
Remove cover and bake uncovered for an additional 30 minutes, stirring halfway through and adding the streusel for the last 15 minutes. Bake until the topping is golden and crunchy. Broil on high for 1-2 minutes if not quite golden top, BUT make sure to watch closely
Serve warm and enjoy!