Preheat oven to 375°F (190°C). Line a large baking sheet with parchment paper or lightly grease it.
In a food processor, combine black beans, salsa, taco seasoning, and garlic powder. Blend until mostly smooth but still slightly chunky. Set aside.
Heat olive oil in a frying pan over medium heat. Add red onion and orange bell pepper. Sauté for about 5 minutes, or until the onion becomes translucent. Remove from heat.
Lay out tortillas on a clean surface. Spread about ¼ cup of the bean mixture on one half of each tortilla. Top with a spoonful of the sautéed veggies and a sprinkle of cheese. Fold each tortilla in half and place it on the prepared baking sheet. Sprinkle a little extra cheese (about 1 tablespoon) on top of each folded taco.
Place in the oven and bake for 15–18 minutes, or until tortillas are golden and slightly crisp, and cheese is melted.
Remove from oven and top with chopped parsley or cilantro. Serve with sour cream on the side, if desired.