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 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.