Place a 9-inch cake pan on the stove over medium heat, then add the butter and brown sugar. Stir gently until the sugar dissolves and the mixture turns a bubbling, golden caramel, filling the pan with a sweet, toasty aroma.
Carefully arrange the pineapple slices in the caramel, placing them in concentric circles. Tuck a maraschino cherry in the center of each ring for a pop of color. The fruit should sit snugly on the caramel, which will be thick and sticky.
Preheat your oven to 350°F (175°C). In a mixing bowl, whisk together the flour, sugar, eggs, oil, and vanilla until smooth and well combined. The batter should be slightly thick but pourable.
Pour the batter evenly over the caramelized fruit in the pan, smoothing the top with a spatula to make sure it covers all the pineapple slices.
Bake in the preheated oven for 35-40 minutes, or until the cake turns a deep golden brown and a toothpick inserted in the center comes out clean. The aroma of vanilla and caramel will fill your kitchen.
Remove the cake from the oven and let it cool for about 10 minutes. Then, place a cooling rack on top of the pan and carefully flip the cake onto the rack, giving it a quick shake or a gentle tap to release it from the pan. The glossy caramel topping with pineapple and cherries should now be on display.
Allow the cake to cool slightly before slicing. The caramel will be sticky and gooey, creating a luscious topping that contrasts with the moist, tender crumb of the cake.
