Prepare the pan:
Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan thoroughly to prevent sticking.
Create the caramel layer: In the bottom of the pan, pour melted butter and evenly sprinkle the brown sugar.
Arrange the fruit:
Place pineapple rings on top of the sugar mixture, fitting as many as possible in a single layer. Add a cherry to the center of each ring.
Prepare the batter:
In a mixing bowl, combine the cake mix, water, oil, and eggs. Mix until smooth.
Assemble the cake:
Pour the batter gently over the pineapple rings and cherries, spreading evenly.
Bake:
Place in the oven and bake for 35–40 minutes, or until a toothpick inserted into the center comes out clean.
Cool and flip:
Allow the cake to cool in the pan for 10 minutes. Place a serving plate on top of the pan, then carefully flip to reveal the caramelized pineapple topping.