In an Instant Pot insert, cook ground beef, onions, and garlic. Turn the pressure cooker on and select SAUTEE. Break it up with a spoon and cook until no longer pink. Drain beef fat; return beef to Instant Pot.
Evenly spread cooked beef/onion mixture across the bottom.
Pour in 1 cup water.
Break spaghetti pasta noodles in half. Layer the noodles like pick-up-sticks. Alternate layers and directions so that the noodles are not sticking together - See post for a photo of this step.
Add 2 teaspoons olive oil to 2 cups water. Pour mixture evenly over the noodles.
In the CENTER of the noodles, pour in canned diced tomatoes. Pour 24 oz. marinara sauce on top in the CENTER. Do NOT STIR (if you stir, you'll get a burn notice) Do not get any tomato ingredients on the sides of the pot either.
Secure lid. Set the pressure valve to SEALING. Select MANUAL or PRESSURE COOK; cook on high-pressure 7 minutes. The pressure cooker will beep and indicate “ON” while it comes to pressure. It took mine about 15 minutes to come to pressure then it started to count down from 7 minutes.
Once done, select CANCEL. Do a QR or QUICK-RELEASE by turning steam release handle to release steam immediately. Once pressure pin drops, open lid and turn off the device.
Stir in 1 teaspoon salt, 1.5 teaspoons Italian seasoning, 1 teaspoon onion powder, and 1/2 teaspoon black pepper.
Serve with parmesan cheese. I like to use the extra 24 ounces marinara sauce to add to each bowl. If you stir the sauce in, the noodles will absorb it so I like to stir in when serving.