Gather the ingredients and preheat your oven to 350F.
For the topping, add the butter to your cake pan and add the sugar on top. Gently dry your fruit and add your pineapple and cherries into your pan on top of the butter and sugar mixture. Chill the pan in the fridge for a few minutes.
For the cake batter, add the flour, salt, baking powder and baking soda to a bowl. Mix well and leave to one side.
In a separate bowl, beat the butter until creamy and then add the sugar. Beat for another minute or so. Add the egg whites, vanilla extract and sour cream; mixing and scraping the sides of the bowl as you go.
Add the bowl of dry ingredients to the main mixing bowl. Then add the juice and milk as you're mixing. Mix until the ingredients are just combined and there are no lumps.
Take out pan from the fridge and add the batter on top. Place in the center of your preheated oven and bake for around 45 minutes.
When ready, remove cake from the oven and leave to cool for around 10 minutes before flipping over and removing your cake from the pan. Serve and enjoy!