Preheat oven to 350°F (177°C) and grease two 9-inch round cake pans.
Whisk together flour, baking powder, baking soda, and salt in a medium bowl.
In a separate bowl, combine buttermilk, pineapple juice, and vanilla extract.
Beat eggs and sugars together on high speed until thick and pale.
Add butter and beat until creamy.
Alternately add dry ingredients and wet ingredients to the sugar mixture, beginning and ending with dry ingredients.
Fold in crushed pineapple and shredded coconut.
Divide batter evenly between pans and bake for 25-28 minutes until a toothpick comes out clean.
Cool cakes completely before frosting.