• Preheat the oven to  170°C/160°C fan/350°F/gas 4. Grease and dust a 9X5 loaf tin with flour.
• Put the sugar, eggs and lemon zest in a large mixing bowl and beat until well combined.
• Sift the flour, baking powder and salt into a separate bowl and set aside.
• Combine milk, sour cream and vanilla extract in a jug. Add one-third of the flour mixture to the sugar mixture and beat well. Then beat in one-third of the milk mixture and beat well. Repeat this process, twice more until everything has been added. 3 additions, ending with flour. Beat until the mixture is light and fluffy.
• Turn the mixer down to low speed, pour in the melted butter and beat until well incorporated.
• Pour the mixture into the prepared loaf tin and bake in the preheated oven for 75 minutes, or until golden brown, and the sponge bounced back when touched.

Lemon Syrup

• Put lemon juice, zest, sugar and water in a small saucepan and bring to a boil over low heat. Raise heat and boil until it is reduced by half and has a thin syrup consistency.
• When the cake comes out of oven, put it on a wire rack and pour the syrup over the top. Leave the cake to cool slightly in the tin before turning out onto cooling rack to cool completely.