Preheat the oven to 350°F.
In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.
Beat the butter with an electric mixer on medium speed for 30 seconds.
Add the sugar and beat until light and fluffy, about 1 minute. Scrape the bowl as needed.
Add eggs one at a time, mixing until incorporated before adding the next.
Mix in the vanilla extract.
Add one-third of the dry ingredients and mix on low.
Add buttermilk and mix until incorporated.
Add another third of the dry ingredients and mix on low.
Pour in the pineapple juice and mix on low.
Add the remaining dry ingredients and mix until just combined. Avoid over-mixing.
Spread the batter evenly over the caramel and pineapple in the pan.