This earthen oven we came across last weekend fascinates me. It was next to the church that Mission was founded on, La Lomita Mission.
The article I linked to here says that you can cook anything in this oven that you would cook in a regular oven as long as you can get it through the door. It says the oven is heated first, the coals scraped out, and then it is ready to be cooked in. http://www.appropedia.org/Blue_ox_earthen_oven