Heat olive oil in a large pot over medium heat. Add the chopped onion and cook for 5 minutes while stirring. Add garlic and stir cooking for an additional minute.
Add salt, pepper, oregano, and sugar. Stir and cook for 1 more minute. Stir in tomato paste.
Pour in the tomato puree, tomato sauce, and chicken broth. Stir and cook for 15 minutes, partially covered with a lid.
Once the soup has cooked, pour in the milk and blend using an immersion blender until smooth.