Prep and sauté the aromatics

Heat 2 tablespoons of the olive oil in a large skillet over medium heat. Add the diced onion, season with a pinch of salt, and cook, stirring occasionally, until the onion is soft and starting to turn translucent, about 4–5 minutes. Add the chopped garlic and cook for another 30–60 seconds, just until fragrant but not browned.

Build the spiced tomato base

Pour in the tomato sauce and stir to coat the onions and garlic. Sprinkle in the chili powder, ground cumin, smoked paprika, and a few grinds of black pepper, stirring well so the spices toast slightly in the pan and bloom in the oil. Let this mixture cook for 2–3 minutes, stirring frequently, until it is thickened and very fragrant.

Simmer the black bean filling

Add the drained and rinsed black beans to the skillet and stir to coat them in the spiced tomato mixture. Pour in the vegetable broth and bring everything to a gentle simmer. Use the back of a wooden spoon or spatula to lightly mash some of the beans, leaving plenty whole; this helps the filling thicken and hold together. Let the mixture simmer for 5–7 minutes, stirring occasionally, until most of the liquid has reduced and the beans are saucy but not runny. Squeeze in the juice of half the lime, taste, and adjust salt, pepper, or spices as needed.

Warm the tortillas

While the bean mixture is simmering, wrap the corn tortillas in a damp paper towel and microwave for about 30 seconds, just until warm and pliable. Alternatively, you can warm them in a dry skillet for a few seconds per side. Warming the tortillas first makes them easier to fold and helps prevent cracking when you crisp the tacos in the pan.

Assemble and crisp the tacos

Spoon a few tablespoons of the black bean filling onto one half of each warm tortilla, spreading it in an even layer and leaving a small border at the edge. Fold the tortilla over the filling to form a half‑moon taco shape, pressing gently so it holds together. Arrange the tacos in a single layer on a large rimmed baking sheet and brush or drizzle both sides lightly with olive oil so they crisp in the oven. Bake at 425–450°F for about 8–10 minutes, then carefully flip the tacos and bake for another 8–10 minutes, until the tortillas are golden brown and crisp and the filling is hot all the way through.

Finish and serve

Transfer the crispy black bean tacos to a plate or wire rack and let them rest for a couple of minutes; this brief cooling time helps the shells firm up and the filling set so they’re easier to eat. Cut the remaining lime into wedges and serve alongside the tacos for squeezing over the top. Add any toppings you like—such as avocado, salsa, slaw, or chopped cilantro—and serve the tacos hot.