Trim the hard/dark stem of the cauliflower, but keep on the green leaves wrapping the head.
Cut the carrots into large chunks and the onion into wedges.
In a small bowl mix the tomato purée, chipotle and garlic with the oil, then add the spices and season with salt & pepper. Rub the cauliflower and its leaves, then the carrot and onion pieces with most of this mixture.
Pour a glass of water into a heavy based, deep pan. Add the remaining paste, mix well, then add the chopped tomatoes, tinned black beans and corn. Combine, then create a well in the middle and put the cauliflower in the centre (stem side down), tucking the carrot chunks around it. Squeeze half of the lime juice over it.
Put the lid on and bake in a preheated oven, at 180°C, for 30 minutes until the cauliflower is cooked through (when you can push a skewer through it- it’s done).
Transfer the cauliflower and carrot pieces to a serving dish. If the bean & corn stew is not thick enough, reduce it on the hob, then spoon it around the vegetables.
Scatter some fresh coriander on top, season with freshly ground pepper then squeeze some lime juice over it and serve.