Start by turning your Instant Pot to the sauté setting. Once hot, add the ground turkey sausage. Cook for about 5-7 minutes, breaking it apart with a wooden spoon until it’s browned and cooked through.
Once the turkey is cooked, pour in the marinara sauce and the canned diced tomatoes. Stir well to combine all the ingredients.
Next, pour in 4 cups of water, then add the whole-wheat spaghetti. Press the spaghetti down gently to ensure it's submerged in the liquid, but don’t worry about it being perfectly flat.
Secure the lid on your Instant Pot and make sure the valve is set to sealing. Select the manual or pressure cook setting and set the timer for 8 minutes.
Once the cooking time is complete, carefully perform a quick release by turning the valve to venting. Be cautious of the steam!
After all the steam has released, open the lid and give your spaghetti a good stir. Serve hot, and garnish with your favorite toppings, like fresh basil or a sprinkle of Parmesan cheese if desired.