Begin by melting the butter in a saucepan over medium heat, then stir in the dark brown sugar. Keep stirring until the mixture turns a deep amber and becomes sticky, filling your kitchen with a sweet, caramel aroma. Once ready, pour this caramel into the bottom of your cake pan, spreading it evenly.
Arrange the pineapple slices neatly over the caramel, placing a cherry in the center of each slice for a colorful touch. Set the pan aside while you prepare the batter.
In a mixing bowl, whisk together the flour, sugar, and a pinch of salt. In a separate bowl, combine the melted butter, eggs, vanilla extract, and milk, whisking until smooth and slightly frothy.
Pour the wet ingredients into the dry ingredients and fold gently until just combined. The batter should be smooth, glossy, and pourable but not runny.
Slowly pour the batter over the arranged pineapple slices, smoothing the top with a spatula if needed. The batter should evenly cover the fruit without disturbing their arrangement.
Place the cake pan in a preheated oven at 350°F (175°C) and bake for about 45 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean. Listen for a gentle sizzle and smell the sweet caramel as it bakes.
Once baked, remove the cake from the oven and let it cool for about 10 minutes. Then, carefully run a knife around the edges to loosen the sides, and place a serving plate on top of the pan.
Quickly but carefully flip the pan over onto the plate, allowing the caramelized fruit to cascade over the top. You should hear a satisfying crack and see the shiny fruit and caramel now on display.
Gently lift the pan away, revealing your beautifully caramelized pineapple upside down cake. Serve warm or at room temperature, enjoying the sticky, gooey topping with each slice.
