Mexican Mac and Cheese

INGREDIENTS:
12 oz dried rigatoni pasta (3 cups)
1 lb. pork sausage
1 cup chopped onion (I used half of a small one)
1 16-oz jar green salsa
2 8-oz pkg shredded Monterey Jack cheese (4 cups)
Optional Toppings:
tomato wedges, sliced jalapenos, chopped fresh cilantro, salsa

DIRECTIONS:

1. Preheat oven to 350 degrees. Lightly grease 3-quart baking dish; set aside. 
2. Cook pasta according to directions. Drain; set aside.
3. Meanwhile, in large skillet cook sausage and onion until meat is browned and onion is tender. Drain fat. Return sausage/onion mixture to skillet. Stir in green salsa.
4. In prepared baking dish, layer half of the cooked pasta, half the sausage mixture, and half the cheese. Repeat layers.
5. Bake, uncovered, for 35 minutes or until bubbly. Let stand 10 minutes. 
6. If desired, top with tomato, jalapeno, and cilantro and serve with additional salsa.