Is it halachically correct to make an oneg shabbos immediately after the shabbos seudah? i.e. Can one decide to bentch and then bring out dessert and cake which will necessitate a bracha achrono. Is this a problem with brocha sheino tzricha?
Although in general it is not correct to bench and then make berachos that would not be required during a meal, if there is a desire to end the meal and to begin an oneg shabbos – which involves a change of atmosphere, and for which people can come and go (and so on), it is fine to do so.
This will not be considered a berachah she-einah tzerichah, because the berachah is indeed required based on the circumstances.
In addition, for cakes and other foods that might require a berachah during the meal, and which often involve some doubt, the idea of benching first is certainly fine, because it actually solves the problem of whether to recite a berachah or not during the meal.