Lemon delicious pudding

1 oz unsalted butter
4 oz caster sugar
1 lemon
2 eggs
1/4 pint milk
1 oz plain flour

Juice lemon and grate zest into bowl.
Add sugar.
Whip egg yolks and add.
Add plain flour.
Melt and then add butter.
Add milk.
Whip egg whites and fold into mix.
Set oven at 180 degrees and cook for 40-45 mins.