Sort through the dried beans and remove stones or damaged beans. Rinse well, soak overnight in plenty of water, and drain; alternatively, boil the beans for 2 minutes, remove from the heat, cover, stand for 1 hour, and drain.

Heat the olive oil in a large Dutch oven or soup pot. Sauté the onion, carrots, and celery for 5 to 7 minutes, until they begin to soften, then add the garlic and cook for about 30 seconds.

Add the drained beans, smoked ham hock, broth or water, bay leaf, chili powder, cumin, and black pepper. Bring the mixture to a boil.

Reduce the heat, partially cover the pot, and simmer for approximately 1 1/2 to 2 hours. Stir occasionally and continue cooking until the beans are tender and the ham is falling from the bone.

Remove the ham hock and pick the meat from the bone. Chop the meat and return it to the soup, adding the optional diced cooked ham at the same time.

Stir in the undrained diced tomatoes and the bean seasoning packet, if provided. Simmer for another 20 to 30 minutes so the tomatoes blend into the broth.

Remove the bay leaf and stir in the lemon juice. Taste carefully and add salt only if needed, then serve hot.