Add the Italian sausage and sauté, breaking up as you cook it, approximately 10 minutes. If the sausage starts to burn, add a bit of water. Add the onion and sauté until it is soft, approximately 2 minutes.
Add the 2 tsp garlic and 1 tbsp Italian seasoning. Stir to combine.
Add the tomato paste and stir. Sauté until it begins to brown; 2-3 minutes.
Add half the water, then the pasta. Rinse the jar out with the remaining water and add to the pot.
Place the lid on the Instant Pot and set the valve to "Sealing." Cook on High for 5 minutes. (The pot will take approximately 10 minutes to come to pressure.)
In the meantime, combine the cheeses with the remaining 1 tbs of Italian seasoning. Leave it on the counter, covered with a cloth.
Natural release for ten minutes, then do a quick quick release.
Remove the lid, stir the pasta and sauce, and then add the cheese in dollops, pushing them under the sauce. Replace the lid and allow it to sit for ten minutes to allow the cheese a chance to melt before serving.