In a medium bowl, lightly beat the egg. Whisk it together with the milk, maple syrup, pumpkin puree, melted butter, and vanilla. In a small bowl, mix together the spices, baking powder, and kosher salt. Whisk to combine the spices and baking powder into the wet ingredients, then stir in the raw steel cut oats. Pour the mixture into the prepared pan.
Cover the pan loosely with foil and bake in the center of the oven for 30 minutes. Uncover the pan and sprinkle with the chopped pecans, then bake an additional 30 minutes until golden brown (60 minutes total).
Serve hot, scooped into bowls, or let cool completely to room temperature and cut into squares for serving. You also can refrigerate and serve cold, which is our favorite way to eat it!