Heat the oil in a medium-sized pan over medium heat, then fry the garlic cloves for 3 minutes until they turn golden; afterwards, add the tahini, vinegar, tomatoes, coriander and cumin; mix them well and leave them for 6 minutes, then add the beans and mix well. Leave them over the heat for 10 minutes until the mixture is incorporated; stirring every once in a while. Add the lemon juice and stir; and then place the beans in a covered serving dish.
Melt two spoons of shortening in a pan over medium heat and spread it over the beans.
Ignite the coals until they are reddened, then place them in a tin foil and leave it open; then place it in the middle of the beans. Cover the dish for 3 minutes until it is steamed, then take out the embers and serve the beans.