Toss shrimp with 1 tablespoon Cajun seasoning; set aside.
Heat butter and oil in a large deep skillet or pot over medium-high heat. Cook shrimp 2-3 minutes per side until pink and cooked through; remove and set aside.
Cook bell pepper in same pot 2-3 minutes until soft. Add garlic; cook 1 minute more.
Stir in fettuccine, broth, cream, tomatoes, and remaining 1 tablespoon Cajun seasoning.
Bring to a boil; reduce to medium. Cook 10-12 minutes, stirring frequently, until pasta is al dente and sauce thickens.
Stir in Parmesan until melted; return shrimp and toss to coat.
Taste and add salt if needed. Garnish with green onions; serve immediately.