Preheat oven to 350°F (175°C). Lightly grease an 8x8-inch or 9x9-inch ceramic or glass baking dish with butter or cooking spray.
In a large bowl, whisk together the rolled oats, baking powder, ground cinnamon, nutmeg, and kosher salt until evenly distributed.
In a separate bowl, whisk together the beaten eggs, milk, pure maple syrup, melted butter, and vanilla extract until smooth.
Fold the diced apples and half of the chopped pecans into the dry oat mixture. Pour the milk-egg custard mixture over the oats and stir gently until combined.
Pour the oatmeal mixture into the prepared baking dish. Scatter the remaining chopped pecans evenly across the top for extra crunch.
Bake for 35 to 40 minutes, or until the top is golden-brown and the center is set (a toothpick inserted into the center comes out clean).
Cool for 5 minutes before slicing into warm squares. Drizzle with warm maple syrup and a splash of cold cream before serving.