Cook pasta on stove as directed on the box. Drain and set aside. This can be done as the meatballs are steaming.
Place steamer basket into the instant pot. Pour in 1 cup water. Add in meatballs. Place lid on instant pot. Set valve to sealed position. Cook on manual or high pressure for 6 minutes. Once the instant pot stops counting release pressure. Remove lid. Remove meatballs to a bowl and cover.
Drain juice from pot insert. Place insert back into the pot. Pour in beef broth and sliced onions. Set to saute mode.
In a liquid measuring cup whisk heavy cream, cornstarch, and seasonings. This will make the cornstarch slurry that will thicken the sauce like a gravy.
Pour cornstarch slurry into the pot witht he beef broth. Bring to a boil on saute mode for about 5 minutes as it starts to thicken turn of pot and let cook for a few minutes. Add meatballs and pasta to the pot and toss well. Taste to see if more pepper or salt is needed.
Serve with fresh rosemary for a little extra flavor.