Prepare the topping: Melt the butter and brown sugar in a sauce pan over medium heat and stir until completely dissolved. Place the pineapple rings into the two prepared 9″ cake pans. Add a cherry inside of each pineapple ring. Divide the topping mixture in two. Pour topping over pineapple slices.
Prepare the cake: Preheat oven to 325 degrees F. Whisk the flour, baking powder, and salt in a large mixing bowl. In a separate bowl, use an electric mixer to beat the sugar and butter together until light. Add eggs one at a time, beating after each addition. Beat in the vanilla. Add dry ingredients alternately with sour cream in 2 additions each, beating well after each addition. Divide batter in half. Pour cake batter over caramel and pineapple in pans.
Bake cake until tester inserted into the center comes out clean, about 35-40 minutes. (See notes if you used a 2″ cake pan – It will take longer to bake if so). Cool cake in pan on a rack for 10 minutes. Turn cake out onto a platter. Serve warm or at room temperature.
