Start by setting your Instant Pot to the sauté function. Once hot, add the olive oil.
Add the diced onion and sauté for about 3 minutes, until softened.
Stir in the minced garlic and cook for an additional 1 minute until fragrant.
Pour in the diced tomatoes (with their juice), vegetable broth, and add the dried Italian seasoning, salt, and black pepper.
Add the penne pasta to the pot, ensuring it is submerged in the liquid.
Close the lid of the Instant Pot and set the valve to sealing. Select the manual setting and set the time for 5 minutes.
Once the cooking time is complete, perform a quick release by carefully turning the valve to venting.
Open the lid and stir the pasta. If the pasta seems a bit saucy, let it sit for a few minutes to absorb the sauce.
Mix in the grated Parmesan cheese until melted through.
Serve hot, garnished with fresh basil leaves if desired.