Cream together the butter and caster sugar until pale, light and fluffy, this will take about 2-3 minutes in a free-standing mixer.
Grate the zest from two of the lemons and add to the mixture. Gradually add the beaten eggs, mixing well between each addition.
Sift together the flour, baking powder and salt. Using a large metal spoon, fold into the cake mixture, then fold in the ground almonds.
Add the milk and the juice from one lemon and mix until smooth.
Spoon the mixture into the prepared tin and level with a palette knife. Bake on the middle shelf of the oven for 45 minutes or until golden brown and a skewer inserted into the middle of the cake comes out clean. Cool the cake in the tin for 15-20 minutes.
. Meanwhile, squeeze the juice from the remaining lemons and mix with the granulated sugar. Spoon the sugary lemon juice over the top of the warm cake and leave in the tin until completely cold