Preheat oven to 425°F. Grease a 13 x 9-inch baking dish or spray with nonstick cooking spray. In the prepared baking dish, stir together the uncooked pasta, sausage, tomatoes, and bell peppers.
In a separate bowl, whisk together the broth, Alfredo sauce, Cajun seasoning, garlic powder, and onion powder.
Pour the sauce mixture into the dish with the pasta and other ingredients. Cover tightly with aluminum foil and bake for 45 minutes.
Uncover; stir. At this point you should check the pasta to make sure that it is al dente (still firm but just about finished cooking). You don’t want it to be tender yet, because it will continue baking in the oven. If the pasta is too hard, cover the dish and return it to the oven until the pasta is al dente. Then move on to the next step.
Once the pasta is al dente, stir in the uncooked shrimp. Sprinkle the cheese over top. Bake uncovered for 5-10 more minutes (I find that 8 minutes is perfect for medium shrimp). The dish is finished when the cheese melts, the shrimp turns pink, and the pasta is tender. Keep a close eye on your shrimp during the final few minutes of baking, because you don’t want to overcook the shrimp and have it turn out rubbery!
Garnish with chopped fresh parsley and sliced green onion, if desired.