Heat a tablespoon of olive oil in a saucepan over medium heat.
When olive oil starts to shimmer, add the garlic and let it simmer for about 10 seconds.
Add cumin and pepper (if wanted) and simmer for another 10 seconds.
Pour in the entire can of beans, don't drain or rinse them.
Simmer for about 15 minutes or until the bean broth has thickened to your liking. If the beans will be the main ingredient of your tacos, cook until the beans are just about totally dry. If you're using them in a mixture (like the Black Bean, Potato, and Onion Tacos ), let the broth stay a little bit runny.