Melt margarine in a heavy large pot over medium-high heat. Add onion and sauté for 4 minutes. Add garlic and ginger, sauté 2 minutes. Add chopped carrots, tomatoes and lemon peel, sauté 1 minute.
Add 3 cups stock and bring to a boil. Reduce heat, cover partially and simmer until carrots are very tender (about 20 minutes).
Cool slightly. Puree soup in batches in the blender. Mix in lemon juice, season with salt and pepper.
To Freeze: Freeze in freezer safe container.
To Reheat: Reheat in a pot or microwave. Serve with a dollop of sour cream.