While I suspect baking could be easily done using Mike Oehler's method* mentioned in his Earth Sheltered SolarGreenhouse Book, I am thinking it would be possible to build a small oven box into the reburn chamber of the RMH. I would think that if someone was good enough at welding to create good seals, it might work just fine to put it on the front of the reburn chamber just above the j-tube so that it opened into the empty space between the feed and the burn chamber itself and would get about the right amount of heat for baking pies and such. Has anyone done anything of this nature yet to test how it might work out?
*So you don't have to read the whole book to find it, the method is setting four nickles on top of the wood burner and then putting a loaf pan on top of those. Over this you would set an inverted metal bowl large enough to cover the whole affair and thus create a makeshift oven and indirect heat convection.
Our oven is made from cast refractory pieces assembled with refractory mortar and added to the build above the J-tube in our castle builds. With a 6" combustion system, it can reach bread temps easily and pizza temps with effort. It is a white oven since the fire is not constructed inside.
You can check out some pictures on our website.