I'm a big fan of Bob
Wells at the youtube channel CheapRVliving.
And they just posted : Cook in Your Car! 12 Volt Electric Oven Cooking in Any Vehicle! Cooking & Warming with NO Propane!
At the end he messed up the units a bit. The cooking probably took about 250 watt hours, or 22 amp hours on a 12vdc system. That'd be a lot of hurt on a lead acid system. On a LiFePo, system i'd probably be fine. Extra fine if you can do it while the sun is out on a few 100 watt pannels.
Bob also mentioned 'wrapping it up' e.g. like a hot box /
hay box cooker.
The given solution depends on situation and budget both in the longer and shorter term.
A $50 cooker that ends up eating $200 batteries every year or two due to deep discharge... not the best plan in the long term, and sometimes you need to do what you need to do.