Preheat oven to 350 degrees F (175 C).

Grease a 7-8 inch cake tin.

Cream together butter and sugar until light and fluffy.

Beat in eggs one at a time, adding a little flour with each egg to prevent curdling.

Add lemon essence.

Fold in the remaining flour until just combined.

Pour the batter into the prepared cake tin.

Bake for 1 1/4 hours.

After half an hour in the oven, place thin slices of Citron peel (optional) on top of the cake.

Let cool in the tin for 10 minutes before transferring to a wire rack to cool completely.