Want to build a portable range top pizza oven box.

[David Fuhrmann]

We are full time RV travelers. I have this idea for building a box that I can sit on top of a RV gas stovetop and make homemade pizzas in. I want it to be 8"-10" high and have a hinged fold down front door. I have a piece of sheetmetal I can use for the top. I am wanting to know if I could make the sides out of wood and cover them with hardie backed board (concrete board typically used to attach tile on) to protect wood frame from getting to hot and catching fire. If not hardie board, what could I use that wouldn't burn or catch fire? I anticipate the internal box temperature may reach 800 degrees. Suggestions?