Heat oil in a sauce pan. Add onion. Sauté 2 minutes. Add tomatoes, broth, salt, and pepper. Stir well. Bring to a boil. Reduce heat, and simmer 7 minutes.
Use an immersion blender to pureé. (If you don't have an immersion blender, pureé in batches in a blender or food processor.)
Cooking Blender
Heat oil in a sauce pan. Add onion. Sauté 2 minutes. Add cooked onions, omatoes, broth, salt, and pepper to a cooking blender. Program for soup.