Preheat your oven to 350 F (175 C). Prepare your jumbo muffin tin by dividing the butter evenly between each tin (about 1 tbsp in each tin, 1 tsp for a regular-sized muffin tin), brushing up along the sides to evenly grease each tin. Next, divide the brown sugar evenly between the tins (about two tbsp in each tin, 1 tbsp for a regular-sized muffin tin) and then add one pineapple ring and one cherry in the center. Press down gently to push the pineapple into the brown sugar butter mixture. Set the prepared pan aside while you make the batter.

Make the batter. In a medium-sized mixing bowl, whisk the butter and sugar together for 2-3 minutes, or until creamy and well combined. Whisk in one egg at a time, followed by the vanilla or rum until well combined.

In a separate bowl, sift or whisk together the all-purpose flour, baking soda, and salt. In a measuring cup combine the pineapple juice and milk right before you are ready to use them. Alternate between 1/3 of the dry ingredients and 1/3 of the pineapple juice milk mixture and mix into the wet ingredients of the batter until everything is just combined and no large lumps remain. Divide the batter amongst the muffin tins, filling up almost the full tin for each one.

Bake for 20-23 minutes (15-17 minutes for a regular sized muffin pan), or until golden brown and a toothpick inserted in the center comes out clean. Let the cakes cool in the pan for 5 minutes, then run the toothpick or a butter knife along the edges to loosen any caramelized bits.

Place a wire baking rack on top of the muffin pan and carefully but quickly flip the pan. You may want to have a towel or something underneath the wire rack to catch any drippings. Carefully shake or tap the muffin pan onto the wire rack until the cakes are free. Serve the cakes warm and enjoy!