Start boiling a large pot of salted water for the pasta.
Rinse and drain the shrimp, then season with 1.5 tablespoons of the cajun seasoning and slice your red pepper and onions.
Cook the pasta according to package directions.
While the pasta is cooking, and the butter to a large skillet and heat to medium heat.
When the skillet is hot and the butter is melted, add the shrimp to the skillet and cook for 2-3 minutes per side depending on the size of your shrimp.
Remove the shrimp from the pan and set aside.
Drain the pasta into a colander.
Add the sliced pepper and onions to the skillet and season with fresh ground pepper. Let the veggies cook while stirring occasionally until they are tender but still crisp - about 5 minutes.
Remove the veggies from the skillet and set aside.
Add the chicken stock, garlic, heavy cream, tomato paste, parmesan cheese and the remainder of the cajun seasoning to the skillet and raise the temperature to high. Gently scrape the bottom on the skillet with a wooden or plastic spoon to release any seasoning stuck to the bottom of it.
When the sauce is boiling, reduce to low heat and simmer until the sauce thickens - about 5 minutes.
Add the pasta to the sauce and toss until it is coated then add the cooked veggies and chopped spinach.
Toss until the greens begin to wilt, then add the shrimp.