Caramelize the onions in a bit of olive oil. Add half of the beans (and all of the dark black liquid) and all of the other ingredients in a food processor and blend until smooth. Add the remaining beans and pulse to just break up the beans. This makes a more rustic dipping sauce. Taste and add more chipotle powder if you want it hotter. Add more salt if needed. You can use to smear on tortillas with any other ingredient or better yet, just grab a bag of tortilla chips and go to town. This is also a good base for huevos rancheros.