There is a well-known divergence of practices between the Ashkenazim and Sepharadim with regard to the prohibition of “Bishul Akum” – eating foods that were cooked by a non-Jew. The custom of the Ashkenazim is to allow eating food cooked by a gentile if a Jew was involved at any stage in the process, even if a Jew simply turned on the oven or stove. Therefore, Ashkenazim will grant Kashrut certification to establishments that employ non-Jewish chefs and cooks, provided that the Mashgi’ah (Kashrut supervisor) or a Jewish employee turns on the stove or oven before the food is cooked.
Sepharadim, by contrast, follow the opinion of the Shulhan Aruch, who does not allow relying on the kindling of the fire. According to Sephardic practice, food cooked by a non-Jew is forbidden unless a Jew placed the food on the stove or in the oven, or if he participated in some significant way, such as by stirring the food. Sepharadim must be aware of this Halacha and of the fact that Ashkenazic Kashrut supervision does not necessarily follow the guidelines that apply to Sepharadim.
However, Hacham Ovadia Yosef, in a famous responsum published in his work Yehaveh Da’at, writes that there is a basis for allowing Sepharadim who eat in restaurants and hotels under Ashkenazic supervision. Even though these establishments rely on the fact that a Jew turns on the stove or oven, there are enough factors that can be taken into account to permit, when necessary, eating in such restaurants or hotels. Certainly, it is preferable to ask the Mashgi’ah to place the food on the fire in order not to rely on the lenient practice of the Ashkenazim. Generally speaking, Kashrut supervisors today are well aware of this subject and, in many instances, an arrangement can be made for Sepharadim so they can follow the more stringent ruling of the Shulhan Aruch. If, however, this is not possible, then there is room to allow eating an establishment that relies on the Ashkenazic custom in this regard.
It must be emphasized, however, that this applies only in hotels and restaurants. In one’s home, this leniency should not be relied upon, and thus one should not eat food cooked by a non-Jewish housekeeper, even if he or another Jew turned on the oven or stove. It should also be noted that at Semahot or other affairs, there is often an “egg station” where a non-Jewish employee of the catering service prepares fried eggs for the guests. It is proper to ask the employee to allow one to pour the eggs onto the stove, or to stir the eggs, so that he would be significantly involved in the process and thus avoid the prohibition of “Bishul Akum.”
Summary: Ashkenazim allow eating food cooked by a non-Jew if a Jew turned on the stove or oven, whereas Sepharadim do not follow this leniency. Therefore, if a Sepharadi eats at a restaurant or hotel under Ashkenazic Kashrut supervision, he should preferably ask that a Jew place his food on the fire or in the oven, in accordance with Sephardic practice. If this is not possible, then one may nevertheless eat at the restaurant or hotel.