Pineapple upside down cake is generally a short cake. Think about it: it's baked in a single pan that you'd normally use for just one layer of a cake. If your cake seeds excessively short (and dense), you may be using dated baking soda or powder. Test baking powder by sprinkling a bit in a glass of water. Test soda by doing the same, but using vinegar. If either one doesn't fizz, toss and replace it.