Preheat your oven to 350°F (175°C) and position the rack in the center of the oven for even baking.
Prepare the caramel base by pouring the melted butter into your 9-inch round cake pan, making sure it coats the entire bottom.
Sprinkle the brown sugar evenly over the melted butter, creating a thin, consistent layer that will caramelize during baking.
Arrange pineapple rings in a single layer on top of the brown sugar mixture—you should fit about 7 rings, with one in the center and six around it.
Place a maraschino cherry in the center of each pineapple ring and in any gaps between rings for that classic look.
In a large mixing bowl, whisk together the flour, granulated sugar, baking powder, and salt until well combined.
Add the vegetable oil, milk, vanilla, and eggs to the dry ingredients and beat with an electric mixer on medium speed for 2 minutes until smooth.
Stir in the reserved ¼ cup pineapple juice to infuse the batter with subtle pineapple flavor.
Carefully pour the batter over the pineapple arrangement, making sure not to disturb the pattern.
Bake for 30-35 minutes or until a toothpick inserted into the center comes out clean and the top is golden brown.
Allow the cake to cool for exactly 5 minutes in the pan—this timing is crucial for successful release.
Run a knife around the edge of the pan to loosen the cake, then place your serving plate upside down on top of the pan.
Quickly but confidently flip the cake over onto the plate and wait 30 seconds before lifting the pan off to reveal your masterpiece.
Let the cake cool for at least 15 minutes before serving to allow the caramel topping to set slightly.