Turn on the Instant Pot and set to Sauté mode. Once it gets hot, add in the oil, ground beef, diced onions, and garlic. Break up the beef into smaller pieces and cook until the meat is brown, or about 5 minutes.
Turn off the Sauté mode and add ½ cup of water or chicken stock. Use a metal spatula to scrape the bottom of the Instant Pot to get all the leftover bits of meat.
Add in the tomato sauce, butter, Italian seasoning, salt and pepper. Stir well to combine all the ingredients.
Break the gluten-free pasta in half and sprinkle on top of the sauce. Do not stir.
Add in the remaining 1 cup of water or stock. Do not stir.
Close the Instant Pot and cook on high pressure for 8 minutes. It should take about 10 minutes to come to pressure.
Once it is done cooking, quick release by opening the valve.
Stir everything well and serve with fresh parsley and grated Parmesan cheese.