Before drinking wine, one of course recites the Beracha of "Boreh Peri Ha’gefen." However, there is an interesting discussion among the Halachic authorities as to whether this Beracha is recited over wine which is "Mebushal" – meaning, it had been brought to a boil. Such wine, quite obviously, is produced from grapes just like ordinary wine, and so we would assume that it requires the standard Beracha of "Gefen." However, the Rambam (Rav Moshe Maimonides, 1135-1204), in discussing the laws of Shabbat, writes that "Mebushal" wine may not be used for Kiddush on Shabbat. This ruling may be understood as an indication that in the Rambam’s view, "Mebushal" wine is not considered wine as far as Halacha is concerned, in which case it should perhaps require the same Beracha as other fruit juices – "She’ha’kol" – and not the special Beracha over wine. By contrast, the Maggid Mishneh commentary to the Rambam’s Mishneh Torah (by Rav Vidal of Tolosa, 1283-1360) explains that the Rambam considered "Mebushal" wine unsuitable for Kiddush despite its having the status of wine. For this reason, the Maggid Mishneh asserts, the Rambam makes the distinction between "Mebushal" wine and ordinary wine only in the context of Kiddush, and not in regard to the laws of Berachot – perhaps indicating that "Mebushal" wine requires the standard Beracha of "Gefen," and differs from ordinary wine only with regard to Kiddush.
Irrespective of this question surrounding the view of the Rambam, the Rif (Rav Yishak Alfasi, Morocco, 1013-1103) explicitly maintained that over "Mebushal" wine one recites "She’ha’kol," and not "Gefen." Other Rishonim (Medieval Halachists), however, including the Ramban and the Rashba, ruled that "Mebushal" wine requires "Gefen" just like ordinary wine.
The Shulhan Aruch (Orah Haim 202), surprisingly, rules in accordance with the position of the Ramban and the Rashba, that the Beracha over "Mebushal" wine is "Gefen." Generally, the Shulhan Aruch’s policy is to accept the majority view among the Rambam, Rif and Rosh (Rabbenu Asher Ben Yehiel, 1250-1327). In this instance, however, he follows a view which is explicitly opposed by the Rif and seemingly opposed by the Rambam. Moreover, when it comes to disputes regarding the recitation of a Beracha, the Shulhan Aruch usually advocates for avoiding the risk of reciting a Beracha in vain. Yet, when it comes to "Mebushal" wine, the Shulhan Aruch rules that one recites "Gefen" – which would be a "Beracha Le’batala" (Beracha recited in vain) according to the Rif and Rambam.
Several explanations have been offered for the Shulhan Aruch’s ruling. One possibility is that even the Rambam, as we saw, might agree that one recites "Gefen" over "Mebushal" wine, notwithstanding his ruling that such wine is disqualified for Kiddush. Secondly, even if the Rambam maintained that the proper Beracha over "Mebushal" wine is "She’ha’kol," he might concede that after the fact, if one recited "Gefen," he fulfills the obligation, since this wine is, after all, produced from grapes. Therefore, the Shulhan Aruch felt that this Beracha should be recited in order to satisfy all opinions. Thirdly, the Tashbetz (Rav Shimon Ben Semah Duran, Algiers, 1361-1444) suggested that the Rambam’s ruling regarding Kiddush refers specifically to wine which was boiled to the point where its flavor and smell transformed, and it became more like a syrup than regular wine. He would agree that in the case of "Mebushal" wine which generally appears and tastes like ordinary wine, its Halachic status is that of regular wine. If so, then it is understandable why the Shulhan Aruch ruled that the Beracha over "Mebushal" wine is "Gefen" – because he refers to "Mebushal" wine which still resembles ordinary wine.
In any event, this is, indeed, the accepted Halacha – that the Beracha over "Mebushal" wine is the same as the Beracha over ordinary wine.
Summary: The Beracha over "Mebushal" wine (wine which had been brought to a boil) is "Boreh Peri Ha’gefen," just like over ordinary wine, even though there are opinions that it cannot be used for Kiddush on Shabbat.