Preheat your oven to 350°F (175°C). Melt butter in a 9-inch cake pan over low heat on the stove, then add brown sugar and stir until combined and bubbly. Spread the caramel evenly across the bottom of the pan.
Arrange pineapple slices over the caramel layer in a single, snug layer, placing maraschino cherries in the centers if using. Carefully set the pan aside while you prepare the cake batter.
In a mixing bowl, whisk together the cake flour, baking powder, and salt. In a separate bowl, beat the eggs, milk, and vanilla extract until well combined.
Add the wet mixture to the dry ingredients and gently fold until just combined. Be careful not to overmix — the batter should be light and slightly fluffy.
Pour the batter evenly over the pineapple slices in the pan, smoothing the top with a spatula. Place the pan in the oven and bake for about 40 minutes, or until the cake is golden and a toothpick inserted in the center comes out clean.
Once baked, remove the cake from the oven and let it cool for about 10 minutes. Dipping the pan briefly in cold water around the edges can help loosen the caramel from the sides.
Place a serving plate over the pan and carefully flip the cake in one confident motion. Gently lift the pan, revealing the caramelized pineapple topping with the glossy, crackling surface.
Allow the cake to cool slightly before slicing. Serve warm or at room temperature, enjoying the sticky, caramelized fruit and tender cake beneath.
