Collect all the ingredients.
Set the oven to 350°F (175°C) to preheat. Lightly coat a 3-quart baking dish with nonstick spray to prevent sticking.
Brown the ground beef in a large skillet over medium heat, stirring occasionally. Once cooked through, drain off any excess fat.
Stir in the chopped onion and bell pepper, cooking for about 5 minutes until they soften and become tender.
Stir in the taco seasoning and water, then let the mixture simmer for about 5 minutes, or until it thickens.
Mix in the diced tomatoes, sour cream, and black beans, stirring until everything is well combined.
Layer 1 1/2 cups of crushed chips evenly at the bottom of the prepared baking dish.
Spread half of the meat mixture evenly over the layer of chips.
Finish by layering 1 ½ cups of crushed chips and 1 ½ cups of shredded cheese on top.
Layer the remaining meat mixture, followed by the last of the chips and cheese, repeating the process.
Place in the preheated oven and bake for about 25 minutes, or until the cheese is melted and the casserole is bubbly.
Garnish with diced tomato, chopped green onion, and fresh cilantro, then serve with a side of salsa and extra sour cream.