Melt butter in a large oven-proof skillet over medium-high heat. Add the sausage, onion, bell pepper, and garlic to the skillet and sauté until the sausage starts to brown and the onions are starting to soften, about 5 minutes.
Add the BUITONI Refrigerated Alfredo Sauce, chicken broth, and Cajun seasoning to the skillet and stir with a wooden or plastic spoon, scraping the bottom of the skillet to loosen any browned bits.
Add the BUITONI Refrigerated Three Cheese Tortellini and diced tomatoes (with their juices) to the skillet and stir. Bring to a boil then reduce heat to medium-low. Cover and cook for 9 to 11 minutes or until pasta is tender.