Pre-heat the oven to 160 fan / 180 C / gas mark 4.

Line a 23cm round springform tin with greaseproof paper (or brownie pan for sheet cake). Brush the inside of the tin all over with a little butter and sprinkle with flour. Tilt the tin around to coat the inside completely with the flour and tip out any excess.

In a large bowl cream the butter and sugar together with an electric whisk or wooden spoon. Gradually incorporate the eggs (around 2 tbsp at a time) mixing well after each addition.

Add the lemon zest, along with 2 tbsp of the lemon juice, and elderflower cordial and mix again.

Sieve the flours together into the bowl and fold into the mixture using a rubber spatula or metal spoon.

Add a splash of milk to the mixture to loosen if necessary. The consistency of the mixture should be that it just falls off a spoon when shaken over the bowl.

Spoon the mixture into the prepared tin and spread to smooth it out into an even layer.

Bake for around 35 minutes until golden, springy to touch and a skewer comes out clean (cooking times may vary depending on tin size - see notes).

Remove the cake from the oven and prick all over using a cocktail stick. Do not remove the cake from the tin.

Mix the remaining lemon juice with granulated sugar to make a syrup and spoon all over the warm cake to make an even layer of drizzle.

Leave the cake in the tin to cool completely before removing and transferring to a serving dish. Keeps for up to 3 days in an airtight container.