First of all, add the lemon rind and juice to the egg yolks, together with the sugar, and whisk until the mixture is slightly thick and creamy.
Now start to melt the butter in the frying pan and turn the heat on the grill to its highest setting.
Whisk the egg whites until stiff, then using a metal spoon lightly and quickly fold them into the yolks.
Now pour the lot on to the foaming butter, then fold and stir a bit to prevent anything sticking to the bottom. After about 10 seconds, place the pan under the grill, so that the top can brown nicely.
Serve immediately straight from the pan.
If you like to make it slightly more spectacular you can warm a small ladle and pour brandy into it. Set light to the brandy, then carry your omelette to the table, pouring the lighted brandy over just before you get there.