Preheat the oven to 160°C. Grease and line with baking paper a 20cm spring form cake tin.
Cream the butter and sugar until light and fluffy. Add the eggs, a little at a time, beating well between each addition. Stir in the lemon zest.
Sift the flour and baking powder together and fold into the butter mixture alternately with the sour cream. Spoon the batter into the tin and place in the oven.
Bake for 60 minutes or until a skewer inserted into the centre of the cake comes out clean.
Pierce the cooked cake all over with a skewer to allow the syrup to be absorbed. Stir the lemon juice and sugar together and spoon or pour over the hot cake. Leave in the tin to cool before removing.
Serve cut in wedges with a large dollop of Puhoi Valley Greek Style yoghurt on the side.