In a large bowl mix the butter and caster sugar together and then add the eggs one by one. Then add the flour in stages and mix until light and fluffy.
Zest and juice the lemons and add ½ to the mixture. Spoon the mixture in the swiss roll tin.
Place into a preheated oven at 180 degrees for 15 – 20 minutes until golden brown. Allow to cool 10 minutes.
Sieve the icing sugar into a bowl and pour in the remaining lemon juice gradually until the icing is runny. If it is too thick add more juice! Allow to set for one hour and then slice and enjoy!