In a large bowl, combine the onion, red pepper, black beans, salt, pepper, and taco seasoning. Toss together. Stir in the Alfredo sauce, milk, and chipotle salsa. Add the cheese and chicken. Pour the pasta into the Alfredo mixture and toss to coat. Pour the pasta mixture into the prepared baking dish. Sprinkle with panko and bake for 35 - 40 minutes until sauce is bubbling and top is golden.