Preheat your oven to 350℉ (175℃) while you prepare the rest of the ingredients.

In a large skillet over medium-high heat, add the ground beef. Use a wooden spoon to break it apart as it cooks, stirring occasionally until browned and no longer pink, about 5-7 minutes. Drain any excess fat before proceeding.

In a medium mixing bowl, combine the biscuit mix and water. Using your hands, mix until a soft dough forms. Coat your casserole dish with cooking spray and evenly press the dough into the bottom and up the sides. Bake in the preheated oven for 5-8 minutes or until just set and lightly golden. Set aside.

Add the chopped onion and red bell pepper to the cooked ground beef in the skillet. Sauté for 4 minutes, stirring occasionally, until the vegetables are softened. Stir in the taco seasoning mix and remove from heat.

Carefully spread the beef and vegetable mixture evenly on top of the pre-baked biscuit layer in your casserole dish.

In another medium bowl, mix together sour cream, mayonnaise, diced green chiles, ¾ cup of shredded cheese, and garlic powder until smooth. Spread this mixture over the beef layer gently.

Place spoonfuls of salsa on top of the sour cream mixture—there's no need to spread it out just yet. Sprinkle the remaining shredded cheese evenly on top.

Return the casserole to the oven. Bake uncovered for about 30 minutes until the casserole is hot and bubbly and the cheese is melted to perfection.