Daily Halacha: Can You Reheat Food with Sauce on Shabbat?

Is it allowed to place dry food with a little sauce on a hot plate on Shabbat?

Yes. It is permissible to place dry meat on a plata (hot plate) on Shabbat, even if there is a small amount of sauce on it. Since the sauce is considered secondary to the main food (in this case, the meat), it does not count as reheating a liquid, which would normally be forbidden.
This is based on the Shulchan Aruch and clarified by Rabbi Ovadia Yosef in Yabia Omer.

Can you ask an Ashkenazi person to reheat a liquid dish that has cooled down?

In halacha, reheating a liquid that has completely cooled is generally considered as if you are cooking it anew, which is a Torah-level prohibition on Shabbat. If someone reheats it to the point that it’s hot enough to scald the hand (yad soledet bo), that would be considered a violation.

However, if the dish has not fully cooled down, and is still warm, one may ask an Ashkenazi person to reheat it. While this is generally stricter in Ashkenazi practice, it may still be permitted under certain conditions.
This ruling is explained in Chazon Ovadia.

These halachot help us honor the sanctity of Shabbat while still enjoying warm food in a way that follows Jewish law.

From the series "Ach Tov VaChesed – Daily Halacha" by Hidabroot