Preheat the oven to 400°F
Spread asparagus, tomatoes, mushrooms, and onions in a thin layer on a baking sheet and drizzle with oil
Roast vegetables in the oven for 15 minutes, until the asparagus is tender. Remove from the oven and set aside.
Cook the pasta according to package directions. Drain and set aside.
In a small pot simmer steak in au jus for about 8 minutes, drain and set aside.
Place the balsamic vinegar in a small saucepan. Simmer over low heat until about ½ cup remains and the vinegar is thick enough to coat the back of a spoon. Stir in the brown sugar and ¼ tsp freshly ground pepper. Remove from heat.
Place the pasta in a large bowl. Add the butter and stir to coat. Add the balsamic and mix well until the pasta is completely coated.
Stir in the steak, asparagus, onions, and tomatoes.
Serve sprinkled with parmesan cheese and enjoy