Preheat oven to 375°F (190°C).
In a skillet over medium heat, cook ground beef until fully browned. Drain excess fat.
Add taco seasoning, water, and diced tomatoes with green chilies to the beef. Simmer for 5 minutes.
Layer a baking dish with two tortillas, followed by a layer of beef mixture, black beans, salsa, and cheese. Repeat layers twice, finishing with cheese on top.
Bake in the oven for 25-30 minutes or until cheese is melted and bubbly.
Let rest for 5 minutes before slicing. Serve with sour cream and garnish with chopped cilantro if desired.