If a person smells a lemon to enjoy its fragrance, is he required to first recite a Beracha?
Generally speaking, a person who smells a fragrant fruit must first recite the Beracha "Baruch Ata Hashem…Ha'noten Rei'ah Tov Ba'perot." At first glance, this requirement should apply equally to lemons, which Halacha classifies under the category of fruits. Even though people do not normally eat lemons straight, as they do other foods, lemons are nevertheless eaten as part of salads and the like, thus rendering them worthy of inclusion in the Halachic category of Perot (fruits). Seemingly, then, one who smells a lemon should be required to recite this Beracha, just as one must before smelling other fragrant fruits.
Rabbi Moshe Halevi, however, in his work Birkat Hashem, cites the Hida (Rabbi Haim Yosef David Azulai, 1724-1806) as distinguishing in this regard between lemons and other fruits. The lemon, unlike other fragrant fruits, is not intrinsically fragrant; the scent is emitted by the fruit's peel, and not by the fruit itself. Therefore, the Hida rules, one cannot recite over lemons the Beracha of "Ha'noten Rei'ah Tov Ba'perot," which refers only to fruits that are intrinsically fragrant.
Hacham Ovadia Yosef, by contrast, in his work Yabia Omer (vol. 9, O.H. 108:26), maintains that one does, in fact, recite this Beracha before smelling a lemon. His son, Hacham Yishak Yosef, in his work Kol Torah (p. 50), explains Hacham Ovadia's ruling by qualifying the aforementioned argument of the Hida. When the Hida distinguished between lemons and other fruits, he referred only to a case where one smells the peel after it had been removed from the lemon. In such a case, one indeed cannot recite the Beracha since he smells only the fragrance of the peel, and not of the fruit itself. But before the peel is removed from the lemon, it is considered part of the actual fruit, and, as such, one who smells and enjoys the peel's fragrance must recite the Beracha. Hacham Ovadia observes that this is the prevalent practice, and this is indeed the proper ruling to follow.
Summary: One who smells a lemon must first recite the Beracha, "Baruch Ata Hashem Elokenu Melech Ha'olam Ha'noten Rei'ah Tov Ba'perot."