Press on the SAUTE button, and brown the beef breaking it up as you go until it's all brown and no longer pink (about 3 minutes).
Add the diced onion, and garlic and cook for 2 minutes. Switch off the SAUTE setting.
Season with taco seasoning, salt, and pepper. Then add tomato sauce, salsa, and pour in the stock.
Add the pasta over the ground beef, and with a spatula push it in the liquid so it's all covered. If necessary add a little bit of water to cover it.
Cover the Instant Pot with the lid and set the valve on SEALING position. Press on PRESSURE COOK or MANUAL on high for 4 minutes.
Allow the Instant Pot to come to pressure, and cook. Once the cooking has finished, quickly release the steam.
Give the pasta a quick stir, then stir in the heavy cream and cheese until the cheese has melted. Serve warm.