Learn גמרא דף לט. “ולא יפקיענה בסודרין (five lines from top of the Amud) until “ולא יטמיננה בחול (next set of two dots)
Question:
Why is it permitted to cook directly from the heat of the sun?
See רש”י דף לט. “דשרי who says “דאין דרך בישול בכך
Major Question:
We have a rule in ה’ שבת when a melacha is performed in an abnormal way it is exempt from Torah violation however it is still prohibited מדרבנן. Why is it permitted to cook directly from the heat of the sun?
Learn אגלי טל מלאכת אופה ס”ק מד
https://hebrewbooks.org/pdfpager.aspx?req=14401&st=&pgnum=264
https://hebrewbooks.org/pdfpager.aspx?req=14401&st=&pgnum=265
Learn אגרות משה או”ח חלק ג ס’ נב
https://hebrewbooks.org/pdfpager.aspx?req=919&st=&pgnum=351
https://hebrewbooks.org/pdfpager.aspx?req=919&st=&pgnum=352
If someone cooks the קרבן פסח in חמי טבריא did they violate the prohibition of cooking קרבן פסח in water?
See גמרא פסחים דף מא
https://hebrewbooks.org/shas.aspx?mesechta=4&daf=41&format=pdf
If someone cooks meat and milk together in חמי טבריא did they violate the prohibition of cooking בשר בחלב?
See רמב”ם ה’ מאכלות אסורות פרק ט הלכה ו
https://hebrewbooks.org/pdfpager.aspx?req=58960&st=&pgnum=133
Based on the above would cooking in a microwave be a violation from the Torah, Drabanan, or permitted barring the operation of electric appliance on Shabbos
See שו”ת מנחת שלמה קמא ס’ יב הערה ו & ז for a new explanation different than the אגלי טל and אגרות משה
https://hebrewbooks.org/pdfpager.aspx?req=15096&st=&pgnum=149
https://hebrewbooks.org/pdfpager.aspx?req=15096&st=&pgnum=150