Preheat oven to 180 degrees Celsius. Grease a loaf pan 9"x4" or about 22x11cm with butter and line the bottom of the pan with parchment paper
Sift the flour and bicarbonate of soda and set aside
In a large bowl beat the butter and sour cream together for at least 1 minute, using an electric hand mixer. Rub the lemon zest into the sugar. Add it to the butter mixture and beat for 4 minutes until it's light in color. You can beat this on a medium speed
Mix in the eggs, one a time. Ensure it is well incorporated
Mix in the lemon and juice
Add the flour, half at a time. Using the electric mixer, mix until combined, on a low speed. Do not be tempted to over mix.
Pour the batter into the loaf pan. Use a spatula and smooth the top. Bake for 45 minutes or until a toothpick inserted in the center comes out clean.
Allow cake to cool completely before turning it onto a cooling rack