Preheat the oven to 350 degrees F. Lightly grease a 3-quart baking dish.
Bring a large pot of water to a boil and cook the pasta according to package directions. Drain and set aside.
While the pasta is cooking, heat a large skillet to medium-high heat. Add the sausage and onion and cook while breaking up the meat into chunks with a spatula until the meat is browned and the onion is tender.
Drain off any excess grease. Stir in green salsa.
In the prepared baking dish layer half of the cooked pasta, half of the sausage mixture, and half of the cheese. Repeat layers ending with a layer of cheese.
Place into the oven and bake uncovered at 350 degrees F. for 35 minutes or until bubbly. Remove from the oven and let stand for 10 minutes. Top with tomato wedges, jalapeno slices, and cilantro.