In a large mixing bowl, whisk together the flour, baking powder, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl using a handheld mixer, cream the butter, granulated sugar, and brown sugar together until light and fluffy (about 4-5 minutes). Mix in the eggs, one at a time, until fully combined. Then, mix in the vanilla extract and sour cream until well combined, making sure to stop and scrape down the sides of the bowl as needed.
Whisk together the pineapple juice and milk.
With the mixer on low speed, mix in the dry ingredients in three additions, alternating with the milk and pineapple juice.
Pour the batter into the cake pan on top of the pineapple slices and cherries and spread it around into one even layer.
Bake for 45 to 55 minutes or until a wooden toothpick inserted into the center of the cake comes out clean. If needed, tent with aluminum foil for the last 10 to 15 minutes of baking to prevent excess browning.
Remove the cake from the oven and allow to cool for about 10 minutes in the pan, then invert onto a wire rack and remove from the pan to finish cooling.