Set your Instant Pot to sauté mode and heat the olive oil until shimmering, about 1 minute. Add the ground turkey and cook for 1-2 minutes, breaking it apart with a spoon as it browns—you want it mostly cooked through but not fully rendered. Stir in the diced onion, minced garlic, Italian seasoning, oregano, red pepper flakes, and a pinch of salt and black pepper. Sauté for another 2-3 minutes until the onions soften and the spices bloom, releasing their aromas. This layering of flavors creates a much more complex base than simply dumping everything in at once.
Pour in the diced tomatoes with their juice, marinara sauce, and tomato paste, stirring well to combine and break up any paste clumps. Add the uncooked ziti, water, and bay leaf, then stir thoroughly to distribute the pasta evenly throughout the liquid and prevent sticking. I find it helpful to stir one more time just before closing the lid to ensure the pasta isn't clumped on the bottom. The pasta will absorb the sauce as it cooks, so submerging everything well is crucial for even cooking.
Close the Instant Pot lid and set the valve to sealing. Cook on high pressure for 5 minutes. Once the timer beeps, allow the pressure to release naturally for 4 minutes, then carefully switch the valve to venting to quick-release any remaining pressure. Open the lid and stir the pasta—it should be tender and the sauce should coat everything beautifully. If you see any dry spots or the pasta seems underdone, add a splash of water and let it sit with the lid closed for another minute.
Switch the Instant Pot back to sauté mode. Remove the bay leaf, then stir in the shredded mozzarella a handful at a time, stirring constantly until each addition melts completely and creates a creamy, cohesive sauce. Turn off the heat and stir in the ricotta by dolloping it in and gently folding it through—don't overmix, as little ricotta pockets add a wonderful creamy texture. Taste and adjust seasoning with salt and pepper as needed.
Spoon the ziti into bowls or plates. Top each serving with freshly grated parmesan cheese and a generous handful of fresh parsley for brightness and color. The sharp bite of fresh parmesan and the herbaceous parsley help cut through the richness of the cheese and sauce.