Prep the onions and garlic: First you will want to dice your onion, and slice your cloves of garlic. For both of these ingredients, I would suggest that you don’t worry about making them look pretty or be of similar size, as they are all going to be blended up at the end.
Saute the onions, then add the garlic, tomato paste, and flour: Now that the onion and garlic are prepped, get out a 6-quart pot and melt the ½ stick of butter with 2 Tbsps of olive oil. I know to some of you a ½ stick of butter seems like a lot, but trust me it will help create a much creamier soup. Once the butter has melted, add the onions and saute them on medium heat until they are translucent about 5 minutes. Make sure to stir the onions often as you don’t want them to brown up. Then add the garlic and let it cook for another minute, stirring often. Finally, add the tomato paste and flour, stir them in and cook for another two minutes.
Add the broth, tomatoes, and seasonings: Slowly add the broth to the pot in two or three separate batches mixing the tomato paste and flour well after each batch. Then add the tomatoes, sugar, thyme, and optional ingredients and let the mixture come up to a boil.
Let it all simmer uncovered for 30 minutes.
Blend: After the soup has been let to cook for 30 minutes, take the pot off of the heat and blend up all of the ingredients. There are two ways in which you can blend the soup. The first is with a traditional stand-up blender. If you decide to use this type of blender I would suggest that you do it in batches, as blending up to large of a volume at a time can cause a serious mess. The second option is the use of an immersion blender. An immersion blender is definitely the better option as it allows you to blend all of the soup up at once and inside the pot. Whichever option you choose, just make sure to blend up the soup well so that it completely smooth.