Saute Aromatics: Set the instant pot on SAUTE function & set it on HIGH heat. Add oil & when the oil becomes moderately hot gently release the onion & the garlic and saute until they become translucent. Add salt to quicken the process.
Brown the ground Sausage/beef: Add the ground Italian sausage or beef and saute until the color changes. Than, add the bell pepper and mix well. Also, add all the seasonings and brown the meat. This will add huge depth of flavor.
De-glaze Pot: Now, add the chicken stock and de-glaze the pot very well scraping the sides and the bottom of the pot with the help of a spatula. There should not be any stuck food particles at all. This will prevent the BURN error. CANCEL the SAUTE function.
Layer the Ziti & sauce: Now, dump the ziti pasta in a single and even layer. DO NOT stir or mix. Pour the pasta sauce on top of the ziti in a single and even layer. Make sure that the ziti is all covered in the sauce. DO NOT stir. Scoop out the ricotta cheese and add it on top of the sauce. DO NOT stir or mix.
Pressure Cook: Secure the lid of the instant pot, seal the valve and PRESSURE COOK on HIGH for 5 minutes. Once, the cooking cycle is over the instant pot will begin to beep, wait for 4 mins natural pressure release. Than, release the rest of the pressure manually by moving the valve from the sealing to the venting position. Open the lid carefully. You'll find excess liquid on top of the pasta, need not worry it will be absorbed well by the ziti.
Stir cooked Ziti: Hit the KEEP WARM function of the instant pot. Now, gently stir to mix the cooked ziti in the instant pot. As you stir you'll notice that the excess liquid is being absorbed by the ziti.
Add Cheese & Serve: Now, add the parmesan and the mozzarella cheese on top of the pasta in a single and even layer. Secure the lid and allow it to rest for 10 mins. The residual heat will help melt the cheese to form a super cheesy crust. Serve the baked ziti right away. Enjoy!