01 -
Turn Instant Pot to SAUTÉ mode. When it reads 'Hot', add olive oil and chopped onion. Cook until onion is soft, about 3-4 minutes. Add Italian sausage and cook until no longer pink, breaking it up as it cooks.
02 -
Add minced garlic, Italian seasoning, and red pepper flakes. Cook for 1 minute until fragrant, being careful not to let the garlic brown.
03 -
Turn off the Instant Pot. If needed, deglaze the bottom with a little water to remove any browned bits. Add uncooked ziti pasta over the sausage, then pour water over the pasta.
04 -
Pour marinara sauce and diced tomatoes over the pasta. DO NOT STIR - this prevents the pasta from sticking to the bottom.
05 -
Place lid on Instant Pot, ensure valve is set to sealing, and select PRESSURE COOK for 4 minutes. After cooking, do a quick release (or gradual if too much water sprays out).
06 -
When pin drops, carefully remove lid. Stir pasta and sauce together. Add half the ricotta and 1 cup mozzarella, stirring to combine.
07 -
Preheat oven to 350°F. Place half the ziti mixture in a greased casserole dish. Top with remaining ricotta and stir gently until just blended.
08 -
Top with remaining mozzarella and dried parsley. Bake for 20-25 minutes until pasta is bubbling and cheese is melted and golden.
09 -
Let stand for 10 minutes before serving to allow the layers to set. Season with salt and pepper if desired.