Melt ¼ cup butter in a 10 inch cast iron skillet over medium to medium high heat.
Add 1 cup sugar and cook, stirring constantly, for 2 minutes or until sugar is melted and begins to turn golden brown.
Add apple slices, and continue to cook, stirring constantly for 5 minutes or until apples have softened and juices are thickened and syrupy.
Remove from heat and sprinkle the apple mixture with ½ cups of pecans. Set aside.
Beat the remaining ½ cup of butter at medium speed until creamy. Gradually add the remaining sugar, beating until smooth.
Add eggs one at a time, beating until just blended with each additions.
In another bowl, stir together flour, baking powder, and cinnamon. Add to butter / sugar mixture alternating with milk, beating on low until well blended, beginning and ending with flour mixture.
Gently stir in the remaining ½ cup of chopped pecans. Spoon batter evenly over the apple mixture in the skillet.
Bake in a preheated 350 degree oven for 30 minutes or until a toothpick in the center comes out clean. Remove from the oven and allow to cool in the skillet for 5 minutes. Invert cake onto a serving plate.
This is awesome served warm, topped with ice cream and drizzled with caramel sauce.