Preheat your oven to 350°F. In a small, microwave-safe bowl, melt the butter by microwaving it on high power for about one minute. Pour the melted butter into your 9-inch springform pan and use it to grease the sides.

Sprinkle the brown sugar evenly over the melted butter in the pan. Arrange one whole pineapple slice in the center and fan the remaining slices around it. Place a cherry in the center of each pineapple slice.

In a large mixing bowl, whisk together the flour, granulated sugar, baking powder, and optional salt until well combined. Set this mixture aside.

In a separate bowl, whisk together the egg, buttermilk, sour cream, oil, and vanilla extract. Add this wet mixture to the dry ingredients and mix lightly until just combined.

Gently pour the batter over the prepared pineapple slices in the pan. Make sure not to disturb the fruit layout and fill only about ¾ of the pan.

Place the cake pan on a cookie sheet to catch any drips. Bake for approximately 40 minutes or until a toothpick inserted into the center comes out clean.

Allow the cake to cool for at least 30 minutes before inverting it onto a plate. For the best flavor and texture, cover and let it cool overnight before serving.