Heat the oven to 356°F (180 °C). Butter 2 round trays of about a 9″ (22 cm) diameter and cover them with baking paper.
In a large bowl, mix all the dry ingredients - the sifted flour, sugar, cinnamon, baking soda and salt. Separately, beat the eggs, butter, vanilla, mashed bananas and pineapple, add the walnuts at the end.
Homogenize the dry and liquid ingredients and distribute the mixture into the 2 trays. Bake the layers until dry - about 30 min. Let the baked layers cool in the trays.
For the frosting, beat the butter and cream cheese with the mixer on low setting, until the mixture homogenizes. Add the powdered sugar gradually while stirring nonstop. Flavor with the vanilla.
Stick the layers together with the cream and cover the entire cake with it, smoothing it out well. Decorate the Hummingbird Cake with walnuts.