Preheat a griddle pan to high. Peel the onions, scrub the sweet potatoes and deseed the peppers. Cut off a small chunk of each and put aside with one tomato (this is for the salsa later). Roughly chop the rest of the veg into 4cm chunks and halve the remaining tomatoes, then chargrill, working in batches.
Drizzle 1 tablespoon of oil into a large casserole pan over a medium-low heat and stir in the cumin and paprika. Peel, roughly chop and add the garlic, finely grate in the lemon zest, and add the grilled veg bit by bit as they’re ready, stirring regularly.
Tip in the beans (juices and all), and 1 1/2 tins’ worth of water, then add around 1 tablespoon of chilli sauce (or to your liking). Season with sea salt and black pepper and simmer for 30 minutes, or until thickened and reduced. Meanwhile, cook the rice in a pan of boiling salted water according to the packet instructions.
Pick 2 sprigs of mint leaves and very finely chop with the salsa veg, then toss with the lemon juice and season to taste with salt and pepper.
Warm the tortillas on the griddle and ripple a good few shakes of chilli sauce through the yoghurt. Serve the chilli with the black rice, salsa, yoghurt and tortillas, and pick over the mint leaves. Enjoy!