Preheat oven to 180C. Grease a 10cm x 20cm loaf pan and line the base and 2 long sides with baking paper, allowing the sides to overhang.
Use an electric mixer to beat butter, sugar and lemon rind in a bowl until pale and creamy. Add eggs, 1 at a time, beating well after each addition. Add the flour, sour cream and lemon juice, in alternating batches, stirring until just combined. Spoon into the prepared pan and smooth the surface.
Bake for 50 mins-1 hour or until a skewer inserted in the centre comes out clean. Cool in the pan for 5 mins before turning onto a wire rack to cool completely.
To make the lemon icing, stir the icing sugar and lemon juice in a bowl until a smooth paste forms. Spread over the top of the cake, allowing it to drizzle down the sides. Set aside for 30 mins to set. Sprinkle with lemon zest.
