Bring a large pot of salted water to a boil. Add the penne pasta and cook according to package instructions until al dente, about 9-11 minutes. Drain and cool under cold water.

In a large mixing bowl, whisk together mayonnaise, sour cream, Cajun seasoning, lemon juice, garlic powder, and paprika. Season with salt and pepper to taste.

Add the cooled pasta to the dressing, then fold in crab meat, bell peppers, red onion, and celery. Mix gently.

Cover the salad and refrigerate for at least 1 hour to allow flavors to meld.

When ready to serve, stir the salad gently. Garnish with parsley and paprika before serving chilled.