PLACE tomatoes, onion and dressing in blender container; cover. Blend until smooth. Pour into large saucepot. Bring to boil on medium-high heat. Stir in chicken broth. Reduce heat to medium-low; simmer 15 minutes, stirring occasionally. Meanwhile, heat oil in separate saucepan on medium heat. Add noodles; cook 1 minute or until golden brown, stirring constantly. Drain noodles.
ADD noodles and water to tomato mixture in saucepot; cook on medium-high heat 10 minutes or until noodles are tender and about 1/3 of the broth is absorbed. (The noodles should still be somewhat soupy.) Sprinkle with cheese.
TOP each serving with about 1 tsp. of the sour cream; swirl lightly with spoon.