Put the potato in a medium pot over medium heat. Let it boil. Cook for 30 minutes, or until done. Peel and put in a potato blender and mash it well.

Sift the almond with the sugar and a pinch of salt, mixing well to combine.

Transfer mashed potato in a mixing bowl. Add the dry ingredients ( almond, sugar and salt mixture). Gradually stir and mix well for a couple of minutes.

Add the egg, one at a time, rind of lemon, and butter and beat well until well blended and combined.

Pour into the prepared cake tin and bake in the pre heated oven (180°C) for 25 to 35 minutes or until well risen and firm to touch.