Orach Chaim 503 says that one may not prepare from the first day of Yom Tov for the second day of Yom Tov. However, if one is going to eat even one piece of meat on the first day, they may fill up a complete pot and leave the remaining meat for the second day. What I know some people do is warm up food for the children and then leave the remaining food for themselves for the nighttime. My question is: If one warms up food in a oven and then takes a piece out before Shekiya may they return the rest of the food to the oven for the evening meal? If not what can be done in order to warm up food that should be ready by the time one comes home from Shul?
If the food is 1/3 cooked "ochel Ben deruso" then it's not a problem. Because we are not makpid on the rabbinic decree of "ein bishul achar bishul" which literally means "there's no further cooking after the food is already cooked." And this whole concept only applied to shabbat because the rabbis feared that onlookers would see someone put something in the oven or on a stove. Maaras ayin. However for yom tov they were never gozer this because cooking is Mutar bichlal. So onlookers wuldnt assume ur doing it for after the biblical chag (yom tov rishon)