Beat the butter with the sugar and the freshly grated lemon peel with an electric beater or in a stand mixer fitted with the whisk attachment.
Add the butter and sugar alternately and beat for at least 15 minutes until creamy and fluffy.
Slightly beat one egg at a time and pour it into the mixture.
add another egg when you have incorporated the previous one.
Beat the mixture at a low speed until fluffy and smooth.
Sift the flour, the potato starch, the baking powder, and the salt; mix in a spoonful of flour at a time.
The flour has to be completely incorporated before adding another spoon.
Continue to beat with the paddle attachment until smooth and creamy.
Pour the batter into a 9-inch (24cm) springform pan lined with parchment paper.
Pre-heat the static oven to 350°F (180°C) and bake for about 40 minutes.
Be careful not to open the door until the surface becomes golden brown.
Insert a toothpick into the center of the cake: if it comes out clean, your cake is done.
While still hot, release the side of the springform pan and place the cake upside down onto a large flat serving plate, peel away the parchment paper.
let it sit for about 15 minutes (otherwise it will get too moist).
Invert the cake back onto a cooling rack.
Let it cool completely and then generously sift powdered sugar all over the top of the cake.