Preheat oven at 180°C. Sift together the refined flour, baking soda and salt in a bowl. Mix well. Add walnuts and mix well.
Break eggs into another bowl. Add sugar and beat well with an electric beater.
Add vanilla essence, lemon juice, lemon zest and beat again. Add banana puree and beat again. Fold in flour mixture and beat till well blended. Add oil and beat once again.
Pour batter in a silicon mould filling ¾th, tap and place in the preheated oven. Bake for 35-40 minutes. Remove from heat, cool and demould. Slice and serve.