Preheat your oven to 350 degrees F. Grease a 9” cast iron skillet with butter and set aside.
Combine flour, sugar, baking powder, baking soda, and salt in a large mixing bowl.
In a medium bowl, combine milk, ½ cup melted butter, pumpkin puree, the egg, and vanilla extract.
Pour the wet ingredients into the dry ingredients and mix well.
Pour cake batter into the prepared skillet, and use a spatula to smooth the top.
In a small bowl, mix ½ cup of melted butter, brown sugar, and pumpkin pie spice. Pour sugar and spice topping over the cake. Use a butter knife to swirl the mixture into the cake batter in circles.
Bake in preheated oven for 27-30 minutes or until a toothpick inserted into the center comes out clean. Allow the cake to cool for 10 minutes.
For the pumpkin spice icing, add powdered sugar, milk, vanilla extract and ¼ teaspoon of pumpkin pie spice to a small bowl. Stir to combine. Spoon on the icing, slice, serve warm & enjoy!