Preheat the oven to 350F. Grease a 9x13 baking dish.
Pour the butter into the baking dish and add the brown sugar, spreading to evenly cover the entire dish.
½ cup unsalted butter, ⅔ cup packed brown sugar
Place the pineapple rings into the dish over the brown sugar. Place a cherry in the center of each pineapple.
9 slices of canned pineapple, 9 maraschino cherries
Prepare the cake mix with the reserved pineapple juice, butter, and eggs. Pour the batter into the baking dish to cover the pineapple and cherries.
1 box of yellow cake mix, 1 cup reserved pineapple juice, ½ cup unsalted butter, 3 large eggs
Bake for 45-50 minutes or until a toothpick inserted into the center comes out clean.
Place a heatproof plate or platter on top of the baking dish and carefully turn it over. Leave the plate on top for a few minutes to allow the sauce to drain. Remove the baking dish.
Cool the cake for 30 minutes. Serve warm.