360 gr Butter
200 gr Icing sugar
20 gr Lemon zest
120 gr Potato starch
100 gr White flour
Carefully butter and lightly flour a cake tin.
Chop the butter into small pieces, place in a bowl and beat until soft and creamy. Add the icing sugar a little at a time.
Place two egg yolks and a whole egg in a bowl, beat lightly and add to the butter a little at a time, beating vigorously.
While beating, add the lemon zest, then sift in the potato starch, followed by the flour. Blend well into a smooth mixture, pour into the cake tin and place in the oven.