Place beans in a large pot or dutch oven and add water until beans are submerged by 3 to 4 inches. Add the garlic and onion, squeeze in orange juice, then add the squeezed orange halves. Cover and place over high heat until water comes to a boil, then uncover pot and reduce heat to a bare simmer. Cook until beans are completely tender and creamy, 1 to 2 hours, stirring occasionally, and adding water if tops of beans become exposed.
