Whilst searching for power MOSFETs to build a H-bridge, I noticed this 12V microwave oven for in-car use. And whilst the thought of solar-powered cooking did cross my mind briefly, I had to reject it as being ultimately rather impractical. It needs 20 amps even on its low power setting, which is enough to cane one of my 8Ah batteries in 24 minutes.
If I wanted hot food while out and about, I’d be more inclined to consider a Coleman stove. This one is powered by unleaded petrol. It’s well worth the initial investment; petrol works out cheaper in the long run than butane canisters (not to mention there being several different, incompatible types), and is more widely available.
Or if I just wanted to heat up a Cornish pasty, I’d probably wrap it in foil and stick it in the engine compartment!