• Preheat the oven to 325F. Lightly grease one 9-inch round cake pan and set it aside.
• Slice the cucumber in half and remove the seeds with a spoon. Reserve 3-5 slices for garnish, then cut into large chunks then puree in a blender until smooth. Add the lemon zest and juice and mix well.
• In a large bowl, cream the butter and sugar with an electric mixer for 1-2 minutes until light and fluffy. Beat in the eggs, one at a time, then beat in the vanilla.
• In a separate bowl, mix together the flour, baking powder and salt. Stir 1/3 of the flour mixture into the egg mixture, then mix in 1/3 of the cucumber. Repeat until everything is combined and blended together.
• Pour the batter into the prepared pan and bake for 30-35 minutes, until a skewer inserted in the middle comes out clean.
• Leave to cool in the pans for 5 minutes, then turn out onto a wire rack to cool completely.

Icing

• Beat the butter, powdered sugar and gin together with an electric mixer in a medium-sized mixing bowl until smooth and fluffy. Add more powdered sugar or gin, if needed, to reach the consistency of thick yet spreadable frosting.
• Keep in the fridge until ready to ice the cake. Spread the icing over the top of the cake and onto the sides then decorate with the reserved cucumber slices.