5: Pour the milk, while it is still hot, onto the egg yolks through a sieve to remove the lemon zest (which has a rather unpleasant texture in the mouth). Stir to mix thoroughly.
6: Pour the mixture back into the pan, put on low heat and leave to thicken while beating continuously.
7: Once the custard has thickened, leave to cook for 10 minutes uncovered, then add the lemon juice and beat in rapidly with the whisk. Your lemon confectioner's custard is ready.
8: If you want to cool the custard quickly, even very quickly, do it like the professionals. See how in this video.
Remarks
To make a lime version of this custard, simply use a lime instead of the lemon.