How are black beans cooked for Mexican dishes? In the US, some Mexican restaurants and taco vans offer a choice of black beans served as a topping for tacos or tortilla salads. The black beans are not mashed, like refried beans, but served whole.

I bought some dry black beans, but they did not come in any easy-to-prepare can in sauce with instructions. How can I prepare them just as the restaurants do?
Dried legumes, including black benas, are generally soaked in water for at least 8 hours (or overnight) to begin softening them, then drained and simmered in fresh water until tender (usually at least 60-90 minutes). You can add stock or other seasonings during the cooking portion, or add the plain cooked beans into a sauce you've prepared separately.