Preheat the oven to 355 degrees F (180 degrees C). Grease a springform tin with butter and line the base with paper.
Fill a saucepan with water and submerge Lemon (2). Bring the water to the boil and simmer the lemons for 25 minutes or until tender.
Drain the lemons and leave to cool for 15 minutes. Place the lemons in a blender and blitz until smooth.
Whisk the Egg (4) and Caster Sugar (160 gram) together. Beat in the Olive Oil (100 milliliter) followed by the lemon paste. Fold in the Almond Flour (175 gram) and Baking Powder (10 milliliter).
Pour the mixture into the tin and bake on the middle shelf for 1 hour (no fan), or until golden brown.
The cake should have a light springy touch to the top and have shrunken away from the sides of the tin. Leave the cake to cool in the tin.
Zest and juice the remaining Lemon (1).
In a small saucepan over low heat, combine the Caster Sugar (15 gram) with the lemon juice and zest and simmer until the sugar has dissolved.
Use a skewer to prick holes all over the cake and drizzle over the syrup. Leave the cake to cool completely before turning out and serving with whipped cream.