Stir together pasta, water, and salt in the Instant Pot insert. Set to Manual and cook on High pressure for 3 minutes. Quick release pressure when done.
Stir in butter until it is melted. Add cheese, seasoning, and 3 Tbsp milk, stirring until combined.
Once the cheese is melted, check the consistency. If it's too thick, add milk 1 Tbsp at a time until it's the consistency you want. Serve.