Boil the beans in plenty of water, adding salt when they have almost finished cooking, then drain them.
Gently fry the sage in a pan with a little olive oil over a low heat, for a few minutes. Add the beans and the tomato
puree', salt to taste, and then let them blend, stirring them over a moderate heat for ten minutes.
When the tomato has dried completely, the beans are ready.
Pour a little olive oil over them and mix well before serving.