How do you heat food on Shabbat?

Food on Shabbat can only be warmed on a plata (electric hot plate) or a blech (metal sheet over a flame lit before Shabbat). You cannot cook, turn on a stove, or adjust temperatures. The food must be fully cooked before Shabbat — you are merely keeping it warm, not cooking it. This is why traditional Shabbat dishes like cholent (a slow-cooked stew) are prepared before Shabbat and left on the plata throughout.