Heat the olive oil in a large Dutch oven or heavy-bottomed pot over medium heat. Add the finely diced onion, carrot, and celery (the soffritto). Cook, stirring occasionally, for 8-10 minutes, until softened and fragrant but not browned. Add the minced garlic and cook for another minute until aromatic.

Add the diced pancetta to the pot. Cook until it's crispy and the fat has rendered, about 5-7 minutes. This adds a salty, savory depth that is absolutely irresistible.

Pour in the red wine to deglaze the pot, scraping up any browned bits from the bottom with a wooden spoon. Let the wine simmer and reduce by about half.

Pour in the hand-crushed San Marzano tomatoes and their puree. Stir in the tomato paste, dried oregano, red pepper flakes, salt, and black pepper. Add the fresh basil sprig and the Parmesan rind.

Bring the sauce to a gentle bubble, then reduce the heat to low. Cover and let it simmer for at least 2 hours, stirring every 20-30 minutes to prevent it from sticking. The longer it simmers, the richer the flavor will become.

After simmering, remove the Parmesan rind and basil sprig. Taste the sauce and adjust seasoning with more salt and pepper if needed. If the sauce is too acidic, you can add a pinch of sugar to balance it out.