Add pasta and 3 1/2 cups of water to the Instant Pot. Cook on high for 4 minutes and quick release. They will be slightly al dente but that's perfect. Mix. There should still be some water in the bottom.
Add a teaspoon of Sodium citrate and mix. Add two cups of shredded cheese and stir. Cook on high slow cook for about 15 minutes until cheese is melted. If you're in a hurry, use the sauté function but you will need to stir.
When the cheese has melted, add the last cup of cheese to the top and replace the normal lid with the air fryer. Cook at 400 degrees for 8-10 minutes until the top is browned to your liking. Alternately you can put in another pot and broil the cheese, or just mix all the cheese in for a super creamy option. Season to taste.