Sauté the onion: Heat olive oil in a large pot over medium heat. Add the chopped onion and cook until soft, about 5 minutes. Stir often.
Add garlic and tomato paste: Stir in minced garlic and cook for 1 more minute. If using tomato paste, mix it in and cook for another minute to bring out the flavor.
Add tomatoes and broth: Pour in the canned tomatoes with their juices. Add the broth and stir everything together.
Season the soup: Sprinkle in sugar, basil, salt, and pepper. Bring to a gentle boil, then lower the heat and let it simmer for about 15–20 minutes to blend all the flavors.
Blend the soup: Use an immersion blender to puree the soup right in the pot. Or transfer it in batches to a regular blender and blend until smooth. Be careful with the hot liquid!
Add cream: Stir in the cream or milk for a creamy texture. Heat the soup for 2 more minutes without boiling.
Taste and adjust: Taste your soup and adjust the salt, pepper, or herbs if needed.
Serve warm: Pour into bowls and top with fresh basil, croutons, or a swirl of cream. Serve with grilled cheese or crusty bread for the best combo!
Notes
Take time to soften and slightly caramelize the onions before adding anything else. It gives the soup a sweet depth and amazing aroma.