Preheat the oven to 350ºF.
Using a 10-12" cast iron skillet, melt 2 tablespoons of the butter over medium-high heat until the butter starts to bubble.
Add the sliced apples, 2 tbsp of brown sugar and 1/2 tsp pumpkin pie spice until the apples start to soften and the sugar mixture thickens, about 3-5 minutes. Remove from heat and set aside.
In a large mixing bowl, combine the flour, granulated sugar, baking powder, salt, cinnamon, nutmeg and allspice. Set aside.
In a separate mixing bowl combine the milk, egg, melted butter, and vanilla. Add to the flour mixture, stirring to combine.
Pour the cake batter into the skillet over the apples (it will not cover them completely).
Bake the cake for about 50 to 60 minutes, until light brown and a tooth pick inserted into the center comes out clean.
Once cool, dust with confectioners' sugar to serve.