In a medium bowl, combine the peeled shrimp with olive oil and Cajun seasoning. Toss until the shrimp are evenly coated and set aside.

Bring a large pot of lightly salted water to a boil. Add the fettuccini pasta and cook for 8 to 10 minutes, or until al dente. Drain and set aside.

Melt butter over medium heat in a large frying pan. Add the sliced mushrooms and chopped shallots, cooking and stirring until tender, about 5 minutes. Remove from pan and set aside.

In the same frying pan, add the seasoned shrimp. Cook for 2 to 3 minutes per side, or until they turn pink and are just cooked through. Remove from the pan and set aside.

Pour ⅔ cup chicken broth into the frying pan and bring to a boil. Let it cook uncovered until reduced to about ¼ cup, approximately 2 to 3 minutes.

In a small bowl, mix together sour cream and cornstarch until smooth. Stir in the remaining 1 cup of chicken broth, then add this mixture to the reduced broth in the pan. Cook and stir until thick and bubbly, then let it simmer for 1 more minute.

Return the cooked shrimp, sautéed mushrooms, roasted red bell peppers, and capers to the pan. Stir well and heat everything through, about 2 minutes. Season to taste with salt and pepper.

Serve the Blackened Shrimp Stroganoff over the cooked fettuccini.