Step 1: Heat 2 tablespoons of olive oil in a large pot or Dutch oven over medium heat. Add the diced yellow onion and minced garlic. Sauté for 5-7 minutes until the onion is softened and translucent, and the garlic is fragrant.
Step 2: Stir in 1 teaspoon of dried oregano and a pinch of red pepper flakes (if using). Cook for 1 minute more, stirring constantly, to allow the spices to bloom.
Step 3: Pour in the crushed tomatoes, vegetable or chicken broth, 1 tablespoon of sugar, and 1 teaspoon of salt. Stir well to combine. Bring the mixture to a gentle simmer.
Step 4: Reduce the heat to low, cover the pot, and let the soup simmer for 15-20 minutes, allowing the flavors to meld together. If using fresh tomatoes, simmer for 25-30 minutes until very soft.
Step 5: Carefully use an immersion blender to purée the soup directly in the pot until it is completely smooth and creamy. Alternatively, transfer the soup in batches to a regular blender and blend until smooth (be cautious when blending hot liquids).
Step 6: Stir in the 1/2 cup of heavy cream and 1/2 cup of fresh basil leaves. Continue to heat gently for 2-3 minutes, just until the soup is warmed through. Do not bring to a boil after adding the cream.
Step 7: Taste the soup and adjust seasonings as needed, adding more salt, pepper, or sugar if desired. Ladle into bowls and serve hot, garnished with extra fresh basil or your preferred toppings.