I was going to call it a root vege curry, but then I realised potatoes and onions are not officially roots, so I had to go a bit more general.
Your favourite curry powder or paste
(Adjust quantities according to taste and how much room you have in your best thin, dark solar-cooking pot. To maximise heat with my solar cooking equipment, I would not fill my pot much more than half full ... but you are the best judge of your own solar cooker's capabilities.)
Chop onions very thinly. Slices 1-2 cm long and 2-3 mm thick have worked best for me
Chop potatoes and kumara into small cubes.
Chop carrots up however you like them, but smallish.
Throw all veges into the pot, along with plenty of cashew nuts.
Add curry powder/paste and stir round to coat veges.
Mix coconut cream with water till it's a thinly syrupy sort of thickness.
Pour the diluted coconut cream over the veges until it nearly covers them but not quite.
Stir the whole mix some more until the curry is well integrated into the sauce.
Add salt to taste.
Seal it all up, put it in your cooker, and leave in the sun for a day.
Solar cooking info
The basics: how solar cookers work
Instructions and plans for making a host of different solar cookers