Preheat oven to 375°F (190°C). Lightly grease an 8x8-inch or 9x9-inch ceramic or glass baking dish with 1/2 teaspoon melted butter.

In a large mixing bowl, combine the rolled oats, ground cinnamon, nutmeg, baking powder, fine sea salt, and half of the chopped pecans (reserve the remaining pecans for the topping).

Scatter half of the diced apples evenly across the bottom of the prepared baking dish. Pour the dry oat mixture evenly over top of the apples.

In a separate medium bowl, whisk together the milk, pure maple syrup, eggs, melted butter, and vanilla extract until smoothly blended and emulsified.

Pour the liquid mixture slowly and evenly over the oats, ensuring all the oats are moistened and submerged. Scatter the remaining diced apples and reserved chopped pecans over the top.

Bake for 35 to 40 minutes until the top is golden-brown, the edges are lightly crisp, and the center is set (it should feel gently firm to the touch, not liquid).

Remove from oven and let rest for 10 minutes to allow the baked oatmeal to firm up into clean sliceable portions.

Slice into warm squares or scoop directly into breakfast bowls. Drizzle with a generous spoonful of warm pure maple syrup and a splash of cold cream or milk. Enjoy!