Wash the lemon thoroughly. Use dish soap for the first wash, soak in boiling water for 2 minutes for the second wash, scrub with coarse salt for the third wash, and finally clean with baking soda.

Grate the lemon zest carefully, avoiding the white pith. Squeeze the juice from the lemon and set aside.

In a bowl, cream the softened butter and sugar together until light and fluffy.

Add the eggs one at a time, mixing well after each addition. Then, mix in the lemon zest and juice.

Sift the cake flour and baking powder together. Add the dry ingredients to the wet mixture and fold gently with a spatula.

Pour the batter into a greased or lined pound cake tin, filling it about 80% full.