Set oven at 180 C / Gas 4. Grease a 24cm springform tin and line the bottom with baking parchment.
Set aside 1 large bowl and 2 smaller bowls.
Sift flour into smaller bowl. Grate lemon zest into the flour. Juice the lemon and set aside.
Place egg yolks into largest bowl. Place the egg whites in the clean smaller bowl.
Using an electric beater, beat the egg yolks with 100g sugar until light and fluffy. Reduce the speed of the beaters and gradually add the olive oil and lemon juice (save a few drops for the egg whites). Beat until well incorporated. Gently fold in flour and lemon zest.
Add salt and remaining lemon juice to egg whites. Beat for a few minutes. Then add remaining sugar. Keep beating until whites form soft peaks.
Gradually fold the egg whites into the batter until well incorporated. Pour into prepared tin. Sprinkle with caster sugar and bake in middle of the oven for 45 minutes.
The cake is done when a skewer inserted in the centre comes out clean. Let cake cool in tin for a few minutes before releasing the cake.