Preheat oven to 450°F and position oven rack in the center.
Heat 1 tablespoon olive oil in a medium skillet over medium heat. Add diced onion, season with 1 teaspoon kosher salt, and cook until translucent, about 3-4 minutes.
Add garlic and chipotle pepper or adobo sauce; cook until fragrant, about 30 seconds.
Stir in chili powder, ground cumin, smoked paprika, and tomato paste. Cook another 1-2 minutes until aromatic.
Add black beans and stir to combine. Cook until warmed, 1-2 minutes.
Pour in vegetable broth; increase heat to bring mixture to a simmer. Mash black beans slightly with a spatula and cook 1-2 minutes longer to thicken if needed.
Squeeze lime juice into the black bean mixture and season with additional salt and pepper to taste. Remove from heat.
Wrap corn tortillas in a damp paper towel and microwave for 30 seconds to soften.
Brush remaining 2 tablespoons olive oil on a large rimmed baking sheet. Place warmed tortillas on the sheet, coating both sides lightly with oil.
Spread black bean filling on half of each tortilla, then sprinkle cheese on top. Fold tortillas into tacos and carefully place cheese side down on the baking sheet.
Bake tacos for 8-10 minutes, then flip carefully and bake another 8-10 minutes until golden and crispy.
Remove from oven and allow to cool 2-3 minutes; tacos will crisp further.
Serve warm with desired toppings such as cashew crema, cilantro, salsa, and lime wedges.