Add 3 quarts of water to a large pot and bring to boil over medium-high heat.

While water is coming to a boil, cut sausage and asparagus into bite-sized pieces. Slice the sausage into approximately 1/2″ discs and cut each disc in half. Break off the tough ends of the asparagus, and chop each stalk into 4 or 5 pieces.

Heat olive oil in large skillet over medium-high heat. Add garlic and sauté until slightly browned, about 1-2 minutes. Add sausage and asparagus. Sprinkle with Cajun seasoning; stir. Cook, stirring frequently, about 5 minutes.

Cook pasta according to package directions, about 10-12 minutes. Reserve 1/2 cup pasta water. Drain.

Add 1/2 cup pasta water to the sausage and asparagus; stir. Cover; cook about 5 minutes, or until asparagus is tender.

Stir in cooked pasta, tomato sauce and milk. Simmer uncovered for 10 minutes.