You should keep reading.

> She says that they once did a blind test with some customers. They cooked the same cut of beef in a gas oven and in the satellites. “Everyone preferred the second version,” she says. The layer of walnuts, restaurant cooks explain, add smoky notes to the food while also filtering the sun’s rays to aid in even cooking.

So they're altering the recipe / dish layout slightly to accommodate for the different heating style, which alters the flavor.

It is more steamed than baked. All of the moisture is intact which leads to a lot juicier piece of meat. I recommend the GoSun portable unit that is ~$100 to explore cooking with the sun.

Also it looks like they are searing the outside in a way by using the clear dishes over an opaque material that is directly absorbing the infrared heat.

At 700C during an Armenian summer, it is 100% properly baked, not just steamed. That's pizza oven territory ;)

How about an old barrel and some tin foil?