Preheat oven to 180 degrees C. Grease and flour a ring tin.
In a large bowl, mix flour, sugar, bicarb soda, salt and cinnamon. Make a well in the centre and pour in the eggs, oil, vanilla, pineapple, mashed banana and chopped walnuts. Mix well and pour into prepared tin.
Bake in the preheated oven for 75 minutes, or until a toothpick inserted into the centre of the cake comes out clean. Serve hot or cold.