1. Preheat the oven to 180°C. Line a rectangular pound cake tin with baking paper.
2. Peel the bananas and break them into pieces in a small bowl. Using a fork, mash them up until they reach desired consistency. Add lemon juice and sugar. This prevents bananas from turning brown. Put it aside for later.
3. In a large bowl, cream together butter and sugars until smooth and fluffy. Stir in the beaten egg and vanilla extract.
4. Sift flour, baking powder and baking soda into the batter mixture and combine well. Be careful not to overmix.
5. Add mashed bananas and chocolate chips (optional), whisk them to combine evenly.
6. Pour the mixture into prepared tin.
7. Bake it for 40 to 45 mins or until a wooden pick inserted in center comes out clean. Remove from the oven and let the cake cool in the pan for about 10 minutes, and then transfer onto a wire rack. Slice when cool.