Heat 1 tsp. oil in a skillet over medium-high heat. Brown 12 oz. sausage (in batches) on both sides (about 1-2 minutes per side). Drain on a paper towel lined plate.
Boil 8 oz. pasta in salted water according to package. Ladle out (or scoop with a mug) 1/2 cup starchy cooking water and set aside. Drain pasta.
Meanwhile, add 1 tsp. oil, 1/2 onion and 2 bell peppers to the skillet and cook over medium to medium-high heat for 6-8 minutes until tender. Add the 2 cloves garlic and cook another 30 seconds.
Add 1 c. cream, 1 tsp. Cajun seasoning, and 1/2 tsp. salt (only if using a salt-free Cajun seasoning!). Bring to a simmer. Simmer and stir for about 3 minutes until thickened. (If using half-&-half, milk, or substitute- Mix cornstarch with water and add to the sauce. Simmer 1-2 more minutes until thickened.)
Mix the cooked pasta and browned sausage into the sauce along with ~1/4 cup starchy pasta water until combined and sauce clings to pasta. (Add more pasta water if needed to thin out sauce.) Remove from heat, garnish with cilantro, and serve.