Squeeze juice from half of grapefruit to yield about 1/3 cup.
Place graefruit juice, sweetener in small saucepan, bring to boil and allow to simmer until reduced to about 1/4 cup. Add salt, vinergar and oil.
Meanwhile, while mixture is simmering, peel and pith remaining grapefruit half. Finely chop sections and add to vinaigrette.
Delicious served with steamed or blanched broccoli or greens, also with avocado and baby greens.