In a mixing bowl, combine flour, sugar, sugar substitute, lemonjuice, and lemon peel.
In another bowl, beat the egg yolks at high speed until lemon colored.
Add the yolks to the flour mixture.
Beat the egg whites until stiff.
Fold them into the custard mixture.
Pour the pudding into a casserole coated with non-stick cooking spray.
Put the casserole in a pan of hot water in a preheated 350°F (180°C) oven.
Bake for 35-40 minutes.
The top will be lightly browned.