Break a head of cauliflower into small florets, about a quarter size. Bring the cauliflower and water to a boil and stir just only until the moment the cauliflower is not hard (about 5 minutes). Drain it in a colander and put into a bowl. Immediately add about 2 tablespoons of finely chopped onions, salt, pepper, and pour vinegar all over it. After you have done this, stir in sour cream, about 1/2 cup, more or less. You'll know when it is right.