1. Preheat oven to 375°F (190°C).
2. In a skillet, cook ground beef until browned. Drain excess fat and stir in taco seasoning and 1/4 cup water. Simmer for 5 minutes.
3. Add black beans and salsa to the beef mixture, stirring to combine.
4. In a 9×9-inch baking dish, layer tortilla quarters on the bottom. Spread half of the beef mixture on top, followed by half the sour cream and 1 cup of cheese.
5. Repeat layers, finishing with cheese on top.
6. Bake for 20-25 minutes, or until cheese is bubbly and golden.
7. Remove from oven and top with diced tomatoes, green onions, and cilantro. Let rest for 5 minutes before serving.