Preheat oven to 350 degrees Fahrenheit. Coat a baking dish with cooking spray.
Cook ground beef and onion in a skillet until the meat browns and the onion is translucent. Drain well.
Cook pasta according to the package directions. Drain well.
Add cooked pasta and sauce to the meat mixture, stirring well. Pour into the baking dish and bake 25-35 minutes.
Divide the mixture among plates, sprinkling with Parmesan cheese before serving.