Start the evening before cooking with soaking the red beans. Spread them out on a flat surface and discard any broken or discolored beans. Then put the beans into a container, cover them with plenty of water and leave them to soak in the fridge over night. The next day drain your beans and rinse them well. Then cook your beans in plenty of salt water until they are tender. This takes about 45 minutes in a pressure cooker and up to 2 hours in a normal pot. Drain them and let them cool down. Wash your green peppers and slice them finely. Peel the onions and mince them as fine as you can. I always use a blender for this job. It is not really necessary to use red onions in this recipe, but I love their purplish hue and slightly sweet aroma in this dish. Combine the beans with the vegetables in a big bowl. Dissolve the salt, around half a teaspoon, in the vinegar and blend it well with the olive oil. Add chili flakes and black pepper according to your taste. I like this salad with plenty of punch so I always use a lot of both. Pour the dressing over the salad and mix all the ingredients well. Let it rest at least 1 hour in the fridge before serving, so the beans soak up all the flavors of the dressing.