Begin by peeling and dicing the sweet potatoes into 1-inch cubes. In a large pot, bring water to a boil and carefully add the sweet potato cubes. Cook for about 10 minutes until they begin to soften but are not fully cooked; they should hold their shape well. Drain the sweet potatoes and set them aside.

While the sweet potatoes cool slightly, preheat your oven to 350°F (175°C). Prepare a 9x13-inch casserole dish by applying a generous layer of non-stick spray.

In the prepared casserole dish, place the drained sweet potatoes. Peel, core, and dice the apples into 1-inch pieces. Gently fold the diced apples into the sweet potatoes until evenly distributed.

In a separate bowl, combine the melted butter, brown sugar, maple syrup, and pumpkin pie spice. Whisk until smooth. Pour this mixture over the sweet potato and apple mixture, making sure to coat all the pieces.

Place the casserole uncovered in the preheated oven and bake for about 25 minutes until bubbling and golden brown.

After the initial baking, sprinkle the chopped pecans generously over the top. Return the dish to the oven and bake for an additional 5 minutes.