Place the beans in a bowl, cover with water and soak overnight (12 hours).
Rinse the beans and drain in a sieve. Place in a saucepan, cover with water and add the herbs.
Leave to simmer for about 1 hour. Top up the water if needed.
Plunge the tomatoes into boiling water then into ice cold water.
Drain and peel off the skins.
Again, use a slotted spoon to lift it out of the water and cool in ice water.
Remove the skin of the chilled tomatoes using a small kitchen knife.
Coarsley dice the tomatoes.
Peel and finely dice the onions and garlic.
Wash, deseed and finely chop the chilli.
Cook the onions, garlic and chilli in a pan with olive oil until softened. Add the diced tomatoes.
Drain the boiled beans into a sieve, remove the herbs and add to the pan. Cook, stirring, for a few minutes. Season with balsamic vinegar, salt, sugar, cumin and pepper. Serve with tortillas.