Preheat your oven to 375°F (190°C).

In a large skillet over medium heat, add the lean ground beef, chopped yellow onion, and red bell pepper. Cook for about 7-10 minutes, stirring occasionally, until the beef is browned and the vegetables are tender.

Once the meat mixture is cooked, stir in the taco seasoning mix. Then, add a splash of water to the pan, mixing until well combined and the desired texture is achieved. Allow it to simmer for another 2-3 minutes.

In a medium mixing bowl, combine the biscuit mix with the remaining water, sour cream, mayonnaise, and diced green chiles. Mix until just blended to form a thick batter.

Grease a 9 x 13-inch casserole dish with cooking spray. Start by layering the cooked beef and vegetable mixture evenly on the bottom, followed by the biscuit batter. Drizzle the salsa over the top, then sprinkle a generous amount of cheddar cheese.

Place the assembled casserole in the preheated oven and bake for 25-30 minutes, or until the biscuit topping is golden brown and the cheese is bubbling.

Once baked, remove the casserole from the oven and let it cool for about 5-10 minutes before serving.