Beans soak for 4 5 hours in cold water. This water is discharged and pour a new one which covers it with three fingers. Put it on the fire and then boiling for 2-3 minutes remove from heat. The water is discharged, the beans are transferred into a pressure cooker, pour 1 liter of water, put the salt, the oil, onion and red pepper, pan close and put on fire. Once the valve of the pan starts to hiss, reduce to a minimum the fire and boil for 1 hour. Open pan, immediately add the tomatoes and mint - while the dish is hot, stirring to combine flavors and can immediately serve.