Mix flour, baking powder and salt in a medium size bowl; set aside.
In an oven-proof 10" skillet, melt 5 tablespoons of butter over medium heat. Add brown sugar; cook, stirring constantly, 2 minutes.
Add apple slices to the pan and reduce heat to medium-low. Cook for about 10 minutes, stirring frequently until tender. Remove from heat and let cool about 5 minutes.
In a large bowl, using an electric mixer on high speed, beat the 1/2 cup (1 stick) of butter for 1 minutes or until creamy. Add the granulated sugar and continue to beat until light and fluffy.
Add eggs and vanilla and beat until blended. Reduce speed to low. Gradually blend in flour mixture and then cream cheese and milk.
Spoon batter in skillet over apples, spreading to edges with spatula (edges do not have to be sealed). Bake 30 minutes until golden brown. Cool on rack for 20 minutes. Run a spreader or spatula around the edge of skillet and carefully invert onto a serving plate.