Place ground beef, onion, garlic and butter in instant pot. Use the sautee function on the instant pot to brown the beef and cook the onions. Add pasta, chicken broth and water to the pot. Place the lid onto the pot and close the pressure release valve. Set the instant pot to manual, high pressure for 5 minutes.
When cooking cycle has finished, quick release the pressure valve to release steam. Open the instant pot and stir in evaporated milk and cheese until all cheese is melted. Season with salt and pepper.
Serve topped with fresh tomatoes and shredded lettuce.