Grease and flour two 9-inch (23cm) diameter round cake pans. Preheat oven to 350˚F (180˚C).
Combine flour, baking powder, baking soda, and ground cinnamon in a medium sized bowl. Stir to mix.
In a large bowl, add vegetable oil, sugar and eggs. Beat until light and fluffy, about 2 minutes.
Beat in mashed bananas, crushed pineapples, and sour cream. Add dry flour mixture and beat until smooth.
Divide batter between the two cake pans. Bake for 25 to 30 minutes or until wooden pick inserted in the center comes out clean. Allow cakes to cool completely before frosting.
Pineapple Frosting
Beat butter in a bowl until light and fluffy. Add powdered sugar one cup at a time, food coloring, and enough pineapple juice to form a spreadable consistency. Beat until combined.
Spread about ½ cup frosting on the first layer of cake. Place second cake top side up onto frosted layer. Spread frosting on the side and top of cake. Chill cake in the fridge until frosting sets, about an hour.