Heat olive oil in a medium saucepan over medium-high heat.
Add onions, jalapeño (if using), cumin, salt, oregano, and smoked paprika. Stir and saute for 3-5 minutes, until onions have softened and become translucent.
Add garlic and saute for 30 seconds, until fragrant.
Add black beans, tomato paste, and water. Stir to combine and cook for 3 more minutes, constantly stirring to make sure the tomato paste completely dissolves.
Taste and season with more salt if necessary.
Remove from heat and serve in warm corn tortillas topped with shredded lettuce, shredded cheese, and a drizzle of cilantro lime crema or lime juice.
Video
Notes
Adding a jalapeño is completely optional. If you don’t want it spicy but still want to add the jalapeño, remove and discard the seeds and veins.
These tacos are also great with flour tortillas and hard taco shells!