Preheat the oven to 375 degrees F (190 degrees C).
Melt 1 stick butter in the bottom of a cast iron skillet over medium heat, about 3 minutes. Remove from heat and sprinkle brown sugar evenly over butter. Add pineapple slices to the skillet in a decorative layer with a cherry in the middle of each pineapple ring. Set aside.
Sift flour, baking powder, and salt together in a bowl.
Cream sugar and 1/2 cup butter together in a bowl. Add eggs and mix. Add flour mixture and milk in an alternating fashion. Add vanilla extract and mix well. Pour mixture evenly over pineapples in the skillet.
Bake in the preheated oven until cake is golden brown, about 40 minutes.
Let cake cool in the skillet for 10 minutes before inverting onto a serving plate. Serve warm.