It is well-known that the Beracha of "Ha’mosi" recited over bread covers all foods that are eaten subsequently as part of the meal, such as meat, rice, salads and so on. Therefore, one does not recite Berachot over these foods. When it comes to dessert, however, this is not always the case. If one eats fruits of fruit salad for dessert, the dessert is not covered by "Ha’mosi," and he must therefore recite a new Beracha. And thus, for example, if after the meal a person is brought grapes and cantaloupe, he must recite "Ha’etz" over the grapes and "Ha’adama" over the cantaloupe. After dessert, he recites Birkat Ha’mazon, which covers the entire meal, including the dessert. Even though a separate Beracha was required before eating the dessert, the person does not recite a Beracha Aharona, as the dessert is covered by Birkat Ha’mazon.
There is, however, one situation where one would even be required to recite a Beracha Aharona over the fruit eaten for dessert. The Gemara in Masechet Berachot (41) comments that if the table was removed after the meal, before Birkat Ha’mazon, and it was then brought back with dessert, then one would be required to recite Berachot both before and after dessert. It seems that in ancient times people ate on small, portable tables, and it was customary to remove the entire table after the meal. If the table was removed before dessert, Birkat Ha’mazon does not cover the dessert, since the table’s removal signals the end of the meal, and thus the dessert was eaten separately from the actual meal. As such, a Beracha Aharona is required for the dessert.
While at first glance this ruling does not appear to have any application nowadays, as our tables remain in place and are not removed after the meal, it in fact is very relevant even today. The work Nehar Misrayim (p. 13b) rules that this Halacha applies not only to the removal of the entire table, but also to the removal of the tablecloth. Meaning, if after the meal the table is cleared and the cloth is removed, and a new cloth is put on for dessert (or if the dessert is placed directly on the table), one would not only recite a Beracha over the fruit eaten for dessert, but also a Beracha Aharona. In such a case, the fruit is not covered by Birkat Ha’mazon, since it was not eaten as part of the meal.
Hacham Ben Sion Abba Shaul (Israel, 1923-1998), in his Or Le’sion (vol. 2, p. 104), disputes this ruling, arguing that removing the tablecloth from the table cannot be compared to removing the entire table. Hacham Ovadia Yosef, however, in his Halichot Olam (vol. 2, p. 37), accepted the Nehar Misrayim’s ruling. Accordingly, if the tablecloth was removed before fruit was served for dessert, one must recite Berachot both before and after eating the fruit.
There is a debate among contemporary authorities as to the status of disposable plastic tablecloths, which are placed over the actual cloth, with respect to this Halacha. Hacham David Yosef, in his Halacha Berura, writes that removing the plastic covering from the table differs from the removal of the actual tablecloth, and does not signify the formal end of the meal. As such, one would not recite a Beracha Aharona after eating the fruit for dessert. The Yalkut Yosef (English edition, Berachot, p. 70), however, disagrees, and claims that there should be no difference between removing the plastic covering and the cloth (listen to audio recording for precise citation). In either case, the removal signals the end of the meal, such that the dessert should be viewed as separate from the meal and thus necessitates its own Beracha Aharona. In light of this dispute, it is preferable not to remove only the disposable plastic, and to either remove the actual tablecloth, or leave on the plastic for dessert.
Summary: One who eats fruit for dessert after a meal with bread must recite a Beracha before eating the fruit, but does not recite a Beracha Aharona afterward, as it is covered by Birkat Ha’mazon. If, however, the tablecloth was removed from the table before the fruit was served, then one must recite a Beracha Aharona in addition to Birkat Ha’mazon. If one eats with a disposable plastic covering over the actual tablecloth, he should ensure not to remove the plastic without removing the cloth, as it is unclear whether removing only the plastic requires reciting a Beracha Aharona over the fruit.