Preheat your oven to 450 degrees F with a rack positioned in the center.
In a medium skillet over medium heat, add 1 tablespoon of olive oil. Toss in the diced onion and sauté until translucent and fragrant, about 3-4 minutes. Stir in the minced garlic and optional chipotle pepper, cooking for an additional 30 seconds.
Add chili powder, ground cumin, smoked paprika, and tomato paste into the skillet. Stir well and cook for another minute or two. Incorporate the black beans and stir until warmed through. Pour in vegetable stock and bring to a gentle simmer, mashing some beans slightly.
Wrap tortillas in a damp paper towel and microwave for about 30 seconds. This steams them slightly, making them pliable. Set aside while brushing olive oil on your baking sheet.
Brush a large rimmed baking sheet with the remaining olive oil. Arrange warmed tortillas on the sheet, spoon some black bean filling over half of each tortilla, and sprinkle with shredded cheese before folding them closed.
Bake the tacos for about 8-10 minutes until they start getting crispy. Carefully flip each taco over and return to the oven for an additional 8-10 minutes until golden-brown. Let cool slightly before serving.