Heat the olive oil in a large pot over medium heat until shimmering. Add the diced onion with the salt and cook for 4-5 minutes, stirring occasionally, until the onion becomes soft and translucent. This salting technique helps the onion release its moisture and cook more evenly. Add the minced garlic and cook for another minute until fragrant, being careful not to let it brown.

Stir in the tomato paste and cook for 1 minute, allowing it to caramelize slightly against the pot bottom—this deepens the umami flavor. Add the sugar, basil, and red pepper flakes, stirring well to combine. These ingredients work together to balance the acidity of the tomatoes and add complexity; I find this layering of spices before adding the liquid creates a more cohesive flavor profile throughout the soup.

Pour in the canned tomatoes with their juices and the vegetable broth, stirring to combine everything thoroughly. Cover the pot and bring to a gentle simmer over medium heat. Let it simmer for 20 minutes to allow the flavors to meld and the soup to develop deeper, more rounded taste. The covered cooking prevents too much evaporation and helps the spices infuse evenly.

Remove the pot from heat and let it cool for 2-3 minutes. Add the cottage cheese directly to the warm soup. Using an immersion blender, blend the soup thoroughly until completely smooth and creamy—this typically takes 1-2 minutes of continuous blending. If you don't have an immersion blender, carefully transfer the soup in batches to a regular blender and blend until smooth, then return to the pot. I prefer cottage cheese for this soup because it adds significant protein while creating a silky texture better than heavy cream, plus it keeps the soup lighter overall.

Taste the soup and season with additional salt and black pepper to your preference. Gently reheat the soup over medium-low heat if it has cooled significantly, stirring occasionally, until it reaches your desired serving temperature. Ladle into bowls and serve immediately with your preferred toppings.