Begin by heating olive oil in a large pot over medium heat.
Sauté the chopped onions and minced garlic in the pot for about 5-7 minutes or until they become soft and translucent.
Add chopped tomatoes, tomato puree, vegetable stock, sugar, salt, and pepper to the pot. Stir well to combine all the ingredients.
Bring the soup to a boil, then lower the heat to low and let it simmer for 30 minutes. This allows the tomatoes to completely soften.
Remove the pot from heat and let it cool for a few minutes.
Puree the soup until smooth, either by using an immersion blender or transferring the soup to a blender.
Serve the soup hot and, if desired, sprinkle some fresh basil leaves on top.
