Wash the lemon thoroughly and grate the peel with a grater to prepare the zest.
Soften the butter at room temperature, then cream it together with the sugar.
Add the eggs one at a time, mixing well each time.
Sift the cake flour and baking powder, then add to the batter and mix.
Add lemon juice and lemon zest, and mix again.
Pour the batter into a pound cake pan.
Bake in a preheated oven at 170°C (338°F) for 40-45 minutes.
Let the finished cake cool, then brush with sugar syrup if desired.