Soak the beans in plenty of cold water overnight
Drain the beans. Bring a pot of water to a boil, add the beans, and boil them until they are soft enough to have their peels removed, about 10 to 15 minutes. Drain, then remove the peel of each bean (preferably while watching something good on TV).
Place the peeled beans in a crockpot together with the onion, tomatoes, and lentils and cover with water. Cover and cook on low for 12 hours.
Season with salt to taste.
Serve with a drizzle of olive oil, sliced hard-boiled egg, finely chopped parsley and a squeeze of lemon juice.