In a large bowl, whisk together the sugar, baking powder, flour, baking soda, and salt. Create a well in the middle of the dry ingredients.
In a small bowl, whisk the eggs lightly. Add in the buttermilk, vanilla, cooled butter, and pineapple juice. Whisk until combined well.
Pour the wet ingredient bowl into the dry ingredient bowl. Carefully fold together until the flour is incorporated (a flexible spatula is best for this step). The batter will be thick and lumpy.
Spoon dollops of batter into the cake pan (try not to move the pineapple rings). Gently smooth the top of the batter.
Bake for 38-45 minutes depending on your oven. You do not want to over-bake this cake.
Let the cake cool in the pan for 15 minutes. Invert onto a baking sheet/serving platter. Allow to cool to room temperature. Enjoy!