Start by making your soup: Add olive oil to a pot. Once warm add the onion and salt. Cook on low heat for 10 minutes, stirring occasionally to make sure it doesn't burn.
Add the tomato paste, mix it in, and cook for 30 seconds more.
Add the canned tomatoes and vegetable broth. Increase the heat, bring the mixture to a gentle simmer and cook for 30 minutes, while stirring occasionally. Don't bring it to a boil, maintain a gentle simmer throughout the 30 minutes.
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