Set the Instant Pot to “sauté, low heat.” spray oil, add bell pepper, onion, and a pinch each of salt and black pepper. Sauté for 5 minutes, until the vegetables start to soften.
Add the ground beef and brown for 5 minutes. Transfer the veggies and beef to a plate.
Add the milk and pasta to the pot, cover, and cook for 6 minutes on high pressure.
Quick-release the pressure. Stir in the cheese until melted. Return the veggies and beef to the pot, add the tomato, and toss to combine. Serve hot topped with optional herbs.