Combine tomatoes, chicken broth, garlic cloves, and a large slice of onion in a stockpot over medium heat. Bring to a boil, and gently simmer for about 20 minutes to blend flavors.

Remove from heat and run the mixture through a food mill into a large bowl, or pan. Discard any stuff left over in the food mill.

Melt butter over medium heat in the now empty stockpot. Stir in flour to make a roux by cooking, whisking constantly, until mixture turns medium brown.

Gradually whisk in a bit of the tomato mixture to prevent lumps from forming, then stir in the rest.

Season with sugar and salt to taste.

Serve hot and enjoy!