If using meat, turn Instant Pot to saute and let the Instant Pot heat up until it reads Hot.
Add in the ground beef, along with onions and garlic for added flavor. Cook the beef until browned completely, breaking up the meat as it browns. Once the meat is browned, turn Instant Pot off. Remove meat from inner pot, drain off any grease, and reserve for later.
Add in ¼ cup stock and scrape up any browned bits from the bottom of the Instant Pot to prevent a burn warning.
Break spaghetti noodles in half and add in crisscrossing layers in the inner pot of the Instant Pot. This is a very important step because if you do not crisscross the noodles, they may clump together.
Pour in the remaining stock and gently submerge the noodles into the stock. It is okay if they are not fully submerged, the spaghetti sauce will cover the top of the noodles.
Top the noodles with the browned meat, if using, and the tomato sauce.
Place lid on the pressure cooker and be sure vent knob is pointed to sealed. Cook on High Pressure for 5 minutes.
Once cook time has elapsed, let pressure release for 5 minutes naturally. Then release any remaining pressure by using a wooden spoon to knock the vent knob from sealing to venting, being careful to stand away from any steam that may be released.
Open the Instant Pot and stir the sauce and into the noodles. Dish out and serve with Parmesan Cheese if desired.
If using frozen meat, cook frozen ground beef in the Instant Pot first. Remove cooked beef from Instant Pot once cooked and drain off the liquid from Instant Pot. Proceed with the recipe starting with adding noodles into the pressure cooker.Gluten-Free Instant Pot Spaghetti, I have only had success using the Barilla brand of gluten-free spaghetti. Other varieties give off too much starch as they cook in the pressure cooker and ruin the sauce and taste and at times even cause a burn notice.For Vegan or Vegetarian-Friendly Spaghetti omit the meat or use meatless crumbles.Storing Leftovers: Store for 3-4 days in a sealed container in the refrigerator and can be frozen for 3 months. Determining Cook Time: The cook time is determined by cutting the time indicated on the box of spaghetti and cutting it in half. For most brands, this would be equivalent to 5 minutes. For Homemade Spaghetti Sauce, Mix together 24 ounces crushed tomatoes, 6 ounces tomato paste, 2 teaspoons dried oregano, 2 teaspoons minced garlic, ½ teaspoon dried basil, 1 teaspoon garlic powder, 1 teaspoon onion powder, 1 tablespoon sugar, 1 tablespoon olive oil, ¼ teaspoon crushed red pepper flakes, and ¼ teaspoon kosher salt together until well combined and use in place of jarred sauce. See Instant Pot High Altitude Conversion if cooking 2500+ feet above sea level.