Cook the spaghetti squash. Cut the stem off of the spaghetti squash. Using a paring knife make about 10 vents in the spaghetti squash. Place the trivet in your Instant Pot and add 1 cup of water. Add the spaghetti squash. Close the lid and be sure the vent is set to Sealing. Set to high pressure for 20 minutes. Once the 20 minutes is up turn off your pot and let the pressure release naturally for 5 minutes and then carefully quick release.
Preheat the oven. While the spaghetti squash is cooking preheat the oven to 400°F.
Cool and scrape. Using a pot holder or towel remove the squash from the pot. Let it cool for 15 minutes and then using a sharp knife, slice in half long-ways. Remove the seeds from the middle of the squash and then use a fork to carefully scrape the spaghetti squash strands. Reserve the squash halves for later. Place the strands in a large mixing bowl.
Add the cheese and herbs. Add the cream cheese, ricotta and 1 tablespoon of parmesan to the spaghetti squash. Also add the herbs, pesto and garlic. Toss until well combined.
Stuff the squash. Take the two squash halves and place them on a baking sheet lined with parchment paper. Divide the squash mixture between the two halves. Season with salt and pepper.
Bake the squash. Bake the squash halves for 15 minutes. Remove from oven and sprinkle with remaining parmesan cheese.
Broil to melt the cheese. Turn your oven to broil and broil for 4-5 minutes. Keep an eye on the squash as broiler vary and you don't want to end up with burnt squash!