Cook pasta in a large pot of salted boiling water according to package directions until al dente.
While pasta cooks, heat olive oil in a large skillet over medium-high heat.
Add sliced sausage to the skillet and brown for 3-4 minutes per side.
Remove sausage from the skillet and set aside, leaving the rendered fat in the pan.
Add onions and bell peppers to the skillet and sauté for 5 minutes until softened.
Stir in minced garlic and cook for 1 minute until fragrant.
Whisk in Cajun seasoning, heavy cream, and chicken broth, scraping any browned bits from the bottom of the pan.
Bring the sauce to a simmer and cook for 5-7 minutes until slightly thickened.
Reduce heat to low and stir in the Parmesan cheese until melted and smooth.
Return the sausage to the skillet and add the cooked pasta, tossing until thoroughly coated.
Garnish with sliced green onions and serve immediately.