1. Preheat oven to 180C. Line the baking tray with baking paper.
2. Peel lemons (2 only) and add zest to the bowl. Program 1 minute / Speed 10. You may wish to stop and scrape down sides over the course of the minute.
3. Place butter cubes (300g), flour (300g), sugar (300g), eggs (4), lemon juice (from 2 lemons), baking powder (1 Tbsp), salt (1/4 tsp) and vanilla (1 tsp) in the mixer bowl. Program 1 minute / Speed 4.
4. Coat the blueberries (150g) with the corn flour (20g) and set aside in a small bowl.
5. Pour half the batter into the baking tray. Scatter half the blueberries on top of the batter. Pour the remaining batter on top, then scatter the remaining blueberries over the top.
6. Place in the oven and bake for around 60 minutes. This depends on your oven. Test by sticking a wooden skewer in the cake after 45 minutes to see whether it comes out clean. If it does, it is done. If batter sticks to it, bake it for a little while longer.

Lemon syrup:

1. Place lemon juice (from 2 lemons only), caster sugar (3 Tbsp) and water (4 Tbsp) in a medium sized saucepan and bring to boil.
2. Reduce on medium heat for 10 minutes, until the mixture is bubbly and syrupy. Set aside to cool.
3. Take cake out of the oven and immediately drizzle the lemon syrup over the top. Once it has cooled, remove it from the tin.

Lemon icing:

1. In a mixing bowl add lemon juice (from 1/2 lemon only) and icing sugar (250g). Stir well to combine. If the mixture is really stiff, add a bit more lemon juice, bit by bit, because you don't want it to get too runny. It should have the consistency of thick custard.
2. Spread over the cooled cake. Enjoy!