For the cake: Preheat the oven to 350 degrees F. Spray three 9-inch cake pans with nonstick cooking spray and coat the insides lightly with flour, knocking excess out.
Whisk together the flour, cinnamon, baking soda, salt and nutmeg in a large bowl.
Beat together the granulated sugar, oil, coconut flakes, vanilla, eggs, bananas and crushed pineapples in a separate medium bowl. Pour the wet ingredients into the dry ingredients and whisk until completely combined. Fold in the pecans.
Divide the batter among the prepared cake pans. Bake until a toothpick inserted in the center comes out clean or the cakes bounce back when lightly pressed with a finger, 20 to 25 minutes. Allow to cool for 30 minutes before removing from the pans and cooling completely on a wire rack. Once completely cooled, level the tops using a serrated knife.
For the buttermilk frosting: In the meantime, beat the butter in a stand mixer until fluffy, about 2 minutes. Add the confectioners' sugar 1 cup at a time, beating after each addition until smooth and fluffy. Add the buttermilk, vanilla and salt and beat just to combine. Refrigerate until ready to use.
Use the buttermilk frosting to assemble the cake and decorate with dried pineapple rings and coconut chips.