Preheat the oven to 160ºC (fan-bake). Prepare a 24cm loose-bottomed cake tin by lining the base with baking paper, brushing the sides with butter and dredging lightly with flour.
To make the cake, cream the butter, sugar and lemon zest until light and fluffy. Beat in the eggs one at a time.Sift the flour, baking powder and salt together, and fold carefully into the egg mixture.
Add the milk and stir in gently. Pile the mixture into the prepared cake tin.
Bake for 50-60 minutes or until the cake shrinks from the sides of the tin. This can also be made in 6 small loaf tins which would be baked for about 25 minutes.
While the cake is cooking, prepare the topping and the decoration. To make the topping, stir the caster sugar, lemon juice and gin together.
To make the decoration, slice the lemon finely. Melt the sugar in the water, bring to a simmer and gently poach the lemon slices for 10 minutes. Remove slices to drain. When the cake is removed from the oven, pour topping mixture over the hot cake.
Add the lemon slices around the edge of the top of the cake and allow to cool.
Using a brulee torch, gently scorch the top of the cake.
For a serving idea, spoon over a mixture of whipped cream and Greek-style yoghurt. Serves 12 or more.
As an alternative to the scorched lemon slices, dust with Chelsea Icing Sugar.