Boil potatoes and salt in saucepan until fork-tender, about 14-17 minutes. Drain and cover to keep warm.
While potatoes are cooking, prepare sauce. In a large skillet, heat dressing on medium-high heat. Add the onions; cook and stir 5 minutes or until onions are tender. Reduce heat to medium-low. Add tomatoes, sour cream and seasonings; stir until well blended and mixture is warm. Pour sauce over warm potatoes and toss. Serve hot.
Feel free to substitute ⅓ cup chopped onions for the green onions.