Preheat the oven to 350°F.

In a large skillet over medium-high heat, brown the ground beef, breaking it apart as it cooks. Drain any excess fat and set the beef aside.

In a mixing bowl, stir together the biscuit mix and 1 cup water until a soft dough forms. Press the dough evenly into a greased 9×13-inch casserole dish.

Bake the crust for 5 to 8 minutes, until it is set and lightly golden. Remove from the oven.

Return the skillet to medium heat. Add chopped onion and red bell pepper to the cooked beef and cook for about 4 minutes until softened. Stir in the taco seasoning, then remove from heat.

Spread the beef and vegetable mixture evenly over the par-baked biscuit layer.

In another bowl, combine sour cream, mayonnaise, drained diced green chiles, ¾ cup of the shredded cheese, and garlic powder. Mix until smooth. Spread this creamy mixture over the beef.

Drop spoonfuls of salsa over the sour cream layer. Sprinkle the remaining shredded cheese across the top.

Bake the casserole for about 30 minutes, until heated through and bubbly. Let it rest for 5 minutes before serving.