Soften the onion and garlic: Heat the olive oil in a large deep skillet or pot over medium heat. Add the diced onion and cook for 4-5 minutes until soft and translucent, then stir in the garlic and cook for 30 seconds until fragrant.

Caramelize the tomato paste: Stir in the tomato paste and cook for 2-3 minutes, stirring often, until it darkens to a deep brick red and smells sweet instead of sharp. This step is what builds the flavor.

Build the sauce and add the pasta: Pour in the crushed tomatoes and vegetable broth, then stir in the penne, Italian seasoning, salt, pepper, and red pepper flakes if using. Bring to a boil.

Simmer until the pasta is tender: Reduce the heat to a steady simmer, cover, and cook for 13-15 minutes, stirring every few minutes so nothing sticks, until the pasta is tender and most of the liquid has been absorbed.

Stir in the cream and parmesan: Reduce the heat to low and stir in the heavy cream and parmesan until the sauce turns smooth, creamy, and pink. Let it warm through for a minute.

Garnish and serve: Taste and adjust the salt. Top with fresh basil and extra parmesan and serve right out of the pan.