Heat olive oil in a large skillet or pot over medium-high heat. Add sliced sausage in a single layer and cook for 3 to 4 minutes, turning once, until browned on both sides. Remove and set aside on a plate.

In the same pot, add diced bell peppers and onion. Cook for 2 to 3 minutes over medium heat, stirring occasionally, until they begin to soften and pick up the sausage drippings from the pan.

Stir in Cajun seasoning and garlic powder. Cook for 30 seconds until fragrant. Pour in the chicken broth and bring to a steady simmer over medium heat.

Add dry pasta directly into the pot. Stir well to submerge it in the broth. Cook for 10 to 12 minutes, stirring every 2 minutes to prevent sticking, until pasta is al dente and most broth is absorbed. Add a splash more broth if needed before pasta is done.

Reduce heat to low. Stir in heavy cream and Parmesan cheese until the sauce is smooth and creamy. Return browned sausage to the pot and stir to combine. Add spinach if using and stir for 1 minute until wilted.

Taste before adding any salt. The sausage and Cajun seasoning already carry plenty. Adjust with black pepper or cayenne to preference. Garnish with fresh parsley and serve hot.