Separate the eggs and beat the yolks with water, salt, and pepper until foamy.
Fold into the mixture the stiffly beaten whites.
Melt the fat in a heavy frying pan.
Add the eggs and cook at low temperature until the omelet is slightly brown underneath.
Put the pan in a moderate oven (350 F) and bake for about 15 minutes until the omelet is firm.
Fold one half over the other and serve immediately.