Boil separately two pounds beets and one pound potatoes (skinned or unskinned depending on personal preference). When vegetables are cooled sufficiently to handle, peel away beet skin and slice both. Whisk together dressing ingredients: 2/3 cup olive oil, 1/3 cup balsamic vinegar, 3 T. finely minced rosemary, ¼ cup minced onions, salt and pepper to taste. Toss dressing with vegetables. Serve warm or cold.