Drain the soaked beans and boil in plenty of water until tender.

Sauté the onion and carrot in olive oil until softened, add the tomato paste and sauté a few more minutes.

Drain the boiled beans and add to the sautéed vegetables, then add the potato and add enough water to cover. Caution: add the potato only after the beans have softened, otherwise it may fall apart too early.

Cook the mixture over low heat until the liquid reduces slightly, remove from heat and let cool; serve with lemon slices.