Slice the onion and dice the red pepper into cubes. Let the beans drain. Cook 250 ml of water per person and dissolve the vegetable stock cube.
Put the peanut oil in a broad cooking pot and add the onion and the bell pepper. Add the cumin and half of the chili flakes, simmer for 1 minute and then add the tomato puree. Bake again for 1 minute and then add the tomato cubes, the sugar, the red beans and the stock. Bring to a boil and let it cook well.
Pluck the coriander leaves and squeeze the juice of the lime. Warm the tortillas in a dry pan or in the microwave oven. Cut into parts. Store under aluminum foil to keep warm.
Pluck the coriander leaves. Taste and season the chili with lime juice and any extra chili flakes, pepper and salt. Serve with the warm tortillas and sprinkle with coriander and cheddar.