In a wide pot or Dutch oven, heat the olive oil over medium-high heat until shimmering. Add the chopped onions and minced garlic, then sauté, stirring from time to time, until the onions turn golden and tender—this should take around 8 to 10 minutes. The aroma at this stage should be rich and fragrant.

Stir in the Italian seasoning along with a pinch of red pepper flakes to add warmth and complexity. Mix in the tomato paste, coating the onion and garlic mixture thoroughly, and let it cook for about a minute until deepened in color.

Pour in the San Marzano tomatoes along with their juices, using a spoon or spatula to gently break them apart. Drop in the bay leaves and Parmesan rind, then season with 1 teaspoon of kosher salt and a few twists of freshly ground black pepper. Bring everything to a simmer while stirring occasionally to meld the flavors.

Next, add the chicken broth and bring the mixture to a gentle boil. Reduce the heat and maintain a steady simmer for 15 to 20 minutes, allowing the soup to thicken slightly and the ingredients to harmonize. Discard the bay leaves and Parmesan rind once the simmering is complete.

Blend the soup until smooth using an immersion blender directly in the pot, or transfer it carefully in batches to a countertop blender. Once fully puréed, taste and adjust with more salt and pepper if needed.

Ladle the hot soup into bowls, garnish with fresh parsley leaves, and finish with a generous sprinkling of grated Parmesan cheese for a rich, savory finish.