Preheat the oven to 375°F. Coat a 9×13-inch baking dish with nonstick cooking spray
Place the sweet potatoes in a large pot and cover with water. Bring to a boil over medium-high heat, then cook for 5 minutes. Drain well.
Arrange half of the sweet potato slices in the prepared baking dish. Layer half of the apple slices over the sweet potatoes. Repeat with the remaining sweet potatoes and apples.
Add the melted butter, maple syrup, brown sugar, cinnamon, nutmeg, salt, apple cider, and vanilla extract to a small bowl. Whisk until well blended.
Pour the maple mixture evenly over the sweet potatoes and apples.
Cover the baking dish with aluminum foil and bake for 25 minutes.
Remove the foil and sprinkle the pecans over the top.
Bake uncovered for 15 to 20 minutes, or until the sweet potatoes and apples are tender.
Let the casserole rest for 5 minutes before serving.
Notes
Tips and Tricks
Slice evenly - Keep the sweet potato slices close to the same thickness so they become tender at about the same time.Don’t overcook the sweet potatoes first - Five minutes of boiling is enough. They should still be firm since they’ll finish cooking in the oven.Check the center - Test a sweet potato slice near the middle of the baking dish before removing the casserole from the oven.Keep an eye on the pecans - They’re added toward the end so they toast without burning.
Storing and Reheating
Refrigerator - Store leftovers covered in the refrigerator for up to 4 days.Oven - Cover and reheat at 350°F until warmed through. Remove the cover for the last few minutes if you want the pecans to crisp up again.Microwave - Reheat individual portions in the microwave until hot.