In a large non-reactive pot, add 3 tablespoons of extra-virgin olive oil and 2 tablespoons of unsalted butter (if using) over medium-low heat. Allow the mixture to heat until it’s foaming, about 2-3 minutes.

Carefully place the halved large yellow onion, minced garlic (if preferred), dried bay leaf, and fresh basil into the pot. Stir gently and let them cook for about 10 minutes, until the onion becomes soft and translucent.

Pour in the 3 cans of San Marzano tomatoes, including their juices, to the pot and add 1 cup of water if needed for consistency. Season with 2 teaspoons of sea salt and ½ teaspoon of black pepper.

Raise the heat slightly to bring the sauce to a gentle simmer. Once bubbling, reduce the heat to low and cover the pot partially, allowing it to cook for 45-60 minutes.

After simmering, remove the pot from heat and carefully discard the bay leaf and basil sprigs. Taste the sauce and adjust seasoning as needed.

For a smoother sauce, use an immersion blender directly in the pot to blend until creamy. Alternatively, if you prefer a chunkier texture, give it a stir and leave it as is.