Prepare the Oven & Pan
Preheat oven to 350°F (175°C). Grease a standard 12-cup muffin tin well, ensuring all edges are coated.
Make the Caramel Topping
In a saucepan over medium heat, melt the butter. Stir in brown sugar, rum (or vanilla), and salt. Cook until the sugar is dissolved and the mixture is glossy, about 2–3 minutes.
Spoon about 2 tablespoons of the caramel mixture into each muffin cup.
Add Pineapple & Cherries
Place a pineapple ring into each muffin cup over the caramel. If needed, trim pineapple slices to fit.
Place a maraschino cherry in the center of each ring.
Prepare the Cake Batter
In a mixing bowl, beat eggs with granulated sugar and brown sugar until thick and pale.
Add pineapple juice and rum (or vanilla) and mix until combined.
In another bowl, whisk flour, baking powder, cinnamon, salt, and cornstarch.
Gradually fold dry ingredients into wet until just combined.
Assemble & Bake
Spoon the cake batter evenly over the pineapple-cherry layer in each muffin cup, filling almost to the top.
Bake for 20–25 minutes, or until a toothpick comes out clean.
Cool & Invert
Let the cakes cool in the pan for 10 minutes.
Run a knife around the edges, then carefully invert the muffin tin onto a baking sheet or platter. The caramel topping will drizzle down the sides.
Serve & Enjoy
Let cool slightly, then serve warm or at room temperature.