In a large pot over medium heat, melt 2 tablespoons of unsalted butter until it bubbles. Add one diced yellow onion, sautéing for about 5 minutes until softened and translucent.

Next, introduce 3 minced garlic cloves to the pot. Stir for about 30 seconds until fragrant.

Sprinkle in 2 tablespoons of all-purpose flour and mix well to coat the onions and garlic. Cook for 1-2 minutes until lightly golden.

Gradually whisk in one can (28 ounces) of crushed tomatoes and 4 cups of low-sodium broth, mixing until smooth. Add 1 teaspoon of granulated sugar, 1 teaspoon of dried basil, and season with salt and black pepper.

Bring to a gentle boil over medium-high heat, then reduce heat and let it simmer uncovered for about 15-20 minutes.

Using an immersion blender, puree the soup until velvety smooth—around 1-2 minutes.

Return the blended soup to low heat and stir in 1 cup of heavy cream, warming through. Adjust seasoning if necessary.

Ladle the soup into bowls and garnish with fresh basil leaves and grated Parmesan cheese, if desired.