HEAT dressing in large stockpot on medium-high heat. Add onions, carrots and fennel; cook 5 min., stirring frequently. Stir in broth and water. Bring to boil; simmer on medium-low 20 min. or until vegetables are tender, stirring occasionally and adding tomatoes and pepper the last 5 min.
POUR soup, in small batches, into blender; blend until smooth. Pour into serving bowl. Repeat with remaining soup.
TOP with basil.