Grease a 9x13 casserole dish with non-stick cooking spray. Preheat the oven to 350 degrees Fahrenheit.
Crush chips lightly and sprinkle approximately 1 cup across the bottom of the baking dish.
Cook ground beef in a large skillet over medium heat until mostly browned. Add diced onion and diced bell pepper and saute about 5 minutes longer, until vegetables begin to soften.
Add taco seasoning and water and stir to combine. Bring mixture to a simmer and cook for 5 minutes longer, stirring regularly.
Add the Rotel and sour cream to the meat mixture and stir to combine completely.
Gently mix the black beans into the skillet.
Spread half of the meat mixture over the crushed chips in the casserole dish.
Place another layer of crushed chips over the meat. Spread half of the cheese over the chips.
Repeat to layer the remaining meat, chips, and cheese.
Cover with aluminum foil and bake for approximately 20 minutes, until the cheese is melted and the casserole is hot and bubbly.
Garnish with diced bell peppers and/or chopped cilantro, tomatoes, avocado, etc. Serve with additional sour cream.
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Notes
Other topping ideas include cilantro, diced tomatoes, diced avocado, guacamole, salsa verde, hot sauce, and extra chips for dipping and scooping.
You can vary the number of chips used in this recipe - I used about 10 oz. You can reduce the number of chips and still have a very well balanced casserole. If you wanted more chips, I would recommend adding more moisture to the meat mixture - either additional sour cream, salsa, a can of cream of chicken soup, etc. - the chips will draw some of the moisture out of the meat mixture so plan accordingly if increasing the number of chips.
The aluminum foil is helpful to allow the casserole to heat through and prevent the top from drying out - since the cheese is sitting on top of the chips on the top layer, it can dry out quickly. If you want to crisp up the top or brown the top a little, remove the foil and then cook an additional 5 minutes or so.