Soak beans for at least 4-5 hours. Preheat oven to 300° F. Drain beans, cover with fresh water, and bring to a boil for 5 minutes, drain again.
Mix together the molasses, brown sugar, honey, mustard, cayenne, and tamari in a bowl. Add the beans, onions, garlic, and pepper, mix well.
Place in a baking dish and add water to cover the beans. Cover and bake 6-8 hours, or until beans are soft. Check periodically and add more water if needed.