Preheat oven to 180°C (350°F). Line a 23cm x 33cm x 5cm (9x13x2-inch) baking pan with parchment paper on the bottom and up two sides.
Beat the eggs and sugar with an electric mixer for 4 minutes until light and fluffy. Add oil and continue beating until combined.
Sift flour, salt, baking powder, and bicarbonate of soda into the mixture. Add cinnamon, cloves, and nutmeg. Mix briefly just until incorporated.
Gently fold in pineapple, mashed banana, and walnuts. Pour batter into prepared pan.
Bake 40-50 minutes until golden brown and a skewer inserted in the centre comes out clean. Loosely cover with foil halfway through if browning too quickly.
Cool completely on a wire rack before removing from pan.
For frosting: Beat butter and cream cheese until smooth. Gradually add icing sugar and lemon juice. Beat 2-3 minutes until light and fluffy.
Spread frosting over cooled cake. Sprinkle with chopped nuts to decorate.