Harvard Beets

Mix 1/2 cup sugar, 1 Tbsp. cornstarch, and 1/2 tsp. salt. Add 1/2 cup vinegar and 1/3 cup boiling water. Cook until sauce is clear. Add 2 cups freshly cooked, drained, and diced beets. Keep beets and sauce in warm place for 30 minutes. Add 2 Tbsp. butter and serve.