How to Make It
Preheat oven to 350°F. Melt 2 tablespoons of the butter in a 9-inch cast-iron skillet over medium. Remove from heat. Spread brown sugar evenly over melted butter, and arrange apple rings in a single layer on top of sugar. Place a cherry half in center of each apple ring. Set aside.
Beat sugar and remaining 1/2 cup softened butter with an electric mixer on medium speed in a large bowl until blended. Add egg; beat until well incorporated.
Stir together buttermilk and baking soda in a small bowl until baking soda is dissolved. Stir together flour, baking powder, and pumpkin pie spice in a medium bowl; add to sugar mixture alternately with buttermilk mixture, beginning and ending with flour mixture. Beat well after each addition. Spoon batter evenly over apple rings in skillet.
Bake in preheated oven until a wooden pick inserted in center comes out clean, about 40 minutes. Cool in skillet 5 minutes, and carefully invert cake onto serving plate. Serve warm with whipped cream.