On sauté mode, add in your olive oil and onions. Give it a stir for a minute to soften the onions before adding in garlic and ground beef.
Brown the ground beef in the Instant Pot for 2-4 minutes, breaking up large pieces.
Add in a pinch of salt and a splash of your beef stock to deglaze your pot (scrape and loosen any browned bits on the bottom of the Instant Pot with the stock).
Layer in the passata, cavatappi pasta, and finally the rest of your beef stock. Do not stir. Gently pat the pasta into the liquid if needed.
Place on your lid, seal, and select manual and set for 5 minutes.
Quick release when done and stir in basil and parmesan if desired.