Preheat oven to 350°F. Grease and flour a 9-inch round cake pan.
In a medium bowl, mix together the melted butter and brown sugar until combined. Pour the mixture into the prepared pan and spread evenly.
Arrange the pineapple slices on top of the brown sugar mixture in the pan.
In a large bowl, whisk together the flour, granulated sugar, baking powder, baking soda, and salt. In a separate bowl, whisk together the oil, buttermilk, vanilla, and eggs. Pour the wet ingredients into the dry ingredients and stir until just combined.
Pour the batter over the pineapple slices in the pan. Bake for 40-45 minutes or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for 10 minutes before inverting onto a plate or cake stand.
Enjoy!
Interesting Facts
This cake is believed to have originated in the United States in the early 1900s.
This cake is similar to a traditional British cake called "Pineapple Upside Down Pudding".
The pineapple slices on top of the cake caramelize as the cake bakes, giving it a beautiful golden color.