The Best Pineapple Upside Down Cake Ever!

So I made this cake for Grandpa Mackey's 60th wedding anniversary dinner. It looks like it was complicated to bake, but it was sooo easy. I bought two upside down pineapple cake box mixes at the store. I baked them in two 9" round baking dishes. I flipped them over on two plates and then put them in the fridge over night to harden a little so I could stack them.
I then stacked them and filled them with a pineapple buttecream frosting. It was sooo good! To date, Tanner says it is the best cake I have made.
Here is my pineapple buttercream recipe:

1/2 cup butter
4 cups SIFTED powdered sugar
6 Tablespoons well drained crushed pineapple
1 - 2 Tablespoons pineapple juice

Cream butter, and then gradually add the sifted sugar, cream well. Stir in pineapple, and just enough pineapple juice to make it spreadable. If you add too much juice, just at more conf. sugar to thicken it up.