Cut spaghetti squash in half lengthwise. Scoop out seeds and pulp. Place trivet in pot, along with 1 cup of water. Place squash on top of trivet. Lock lid and cook for 2 minutes at high pressure.
Meanwhile… add eggs, seasoned salt, and black pepper to mixing bowl - whisk together. Add evaporated milk and whisk again.
Once cook time is complete, quick-release pressure. Remove squash from pot.
Add butter to a separate large mixing bowl. Using a fork, scrape out flesh from each half of squash, making sure not to get any shell. Add hot squash on top of butter. Mix well until butter is melted and evenly coats squash. Add 8 ounces of cheese to bowl and mix well. Pour in egg/milk mixture and give a good mix.
Pour squash mixture into a large pyrex bowl (1.75 quart). Do not overfill, leaving a little room at the top. Cover bowl with aluminum foil.
Transfer bowl into pot and place on top of trivet. Lock lid and cook at high pressure for 45 minutes. Once cook time is complete, quick-release pressure.
Remove bowl and uncover. Top with remaining 4 ounces of cheese. Place under high broiler for 1-2 minutes, until desired color and/or crispiness is reached.
Allow to cool slightly before serving because it will be hot.
Just a heads up... spaghetti squash is FULL of water, so don't expect this recipe to be completely dry inside. There will be some water. It's just the nature of the vegetable.