Prepare the Filling. In a skillet, heat olive oil over medium heat. Add diced onion and garlic, cooking until softened. Stir in the black beans, cumin, chili powder, and a few tablespoons of enchilada sauce. Cook for 2-3 minutes, then remove from heat.
Assemble the Enchiladas. Spoon the black bean mixture into the center of each tortilla. Sprinkle a generous amount of cheese on top, then roll the tortillas tightly and place them seam-side down in a greased baking dish.
Add the Sauce. Pour the remaining enchilada sauce evenly over the rolled tortillas, making sure they are well-coated. Sprinkle extra cheese on top for a melty, golden finish.
Bake to Perfection. Preheat the oven to 375°F and bake the enchiladas for 20-25 minutes, or until the cheese is fully melted and bubbly.
Garnish and Serve. Remove from the oven and top with fresh cilantro, diced avocado, or a drizzle of sour cream. Serve hot with your favorite sides.