1. Rinse the beans under cold water, sorting out any rocks/particles. Cover in cold water and soak for 6 to 8 hours.
2. Drain the beans and place in a stockpot with the ham hock; cover with fresh water by 2 inches. Add the tomato sauce, chilli powder, brown sugar, white vinegar, garlic, onions, 1 tablespoon salt and 2 teaspoons pepper.
3. Bring to a boil, lower the heat and simmer, adding a little more liquid if the level gets too low, until the beans are tender, 3 to 4 hours. Taste, and season with additional salt and pepper if needed.