Cook onions and garlic. Add diced onions to a large pot and sauté them over medium heat until the onions are tender. Add the minced garlic and continue to cook for 2 minutes.
Tomatoes and Peppers. Add the canned whole tomatoes with the juice , tomato paste, roasted red peppers, broth, and salt to the pot. Bring to a boil and then cover with a lid and reduce the temperature to a simmer. Cook for 30 minutes.
Blend. Once the soup is cooked remove from the heat and use an immersion blender to puree the soup ingredients until the soup is smooth. Add salt and pepper to taste and stir well.