Heat a large skillet over medium-high heat. Add the ground beef and diced onion, breaking up the meat with a wooden spoon. Cook for 6-8 minutes until the beef is browned and the onion is soft. Drain excess fat if needed. Stir in the garlic and cook for 30 seconds until fragrant.

Add the taco seasoning and 1/4 cup water to the skillet. Stir well and simmer for 2 minutes until the liquid reduces slightly. Fold in the black beans and remove from heat. Let cool for 5 minutes so the filling is easier to handle.

In a medium bowl, whisk together the green enchilada sauce, sour cream, and diced green chiles until smooth. This creates a creamy, tangy sauce that coats every burrito.

Preheat your oven to 375°F. Spread 1/2 cup of the sauce mixture on the bottom of a 9x13 inch baking dish. Working with one tortilla at a time, spoon about 1/2 cup of the beef filling down the center. Sprinkle with 2 tablespoons of cheese. Fold in the sides, then roll tightly from bottom to top. Place seam-side down in the baking dish. Repeat with remaining tortillas.

Pour the remaining sauce evenly over the burritos, making sure they are all covered. Sprinkle the remaining 1 1/2 cups cheese across the top. Bake uncovered for 20-25 minutes until the sauce is bubbling at the edges and the cheese is melted and starting to brown in spots.

Let the burritos rest for 5 minutes before serving - this helps them hold together when you scoop them out. Garnish with fresh cilantro and serve hot.