Tomato-Ginger Soup

This is based on a recipe from Ken Hom's Quick & Easy Chinese Cooking. He says in its intro: "This soup is a year-round favorite of mine because it can be made successfully with canned tomatoes, one of the few processed foods I find acceptable, so you need not wait for fresh tomatoes to come into season. Of course, it is delicious made with fresh ripe tomatoes when they are available at a reasonable price, and they also need little preparation and cook quickly. This is a refreshing soup that makes a sparkling first course. On hot summer days, try serving it at room temperature. For a Southeast Asian touch, add 2 tablesppoons lemon juice. The soup reheats successfully." My picky DH really likes it! :)