Annabel Langbein’s South Seas Hollandaise Sauce

New Zealand food authority Annabel Langbein prepares this rich sauce for poached or broiled fish, although it’s equally delicious on new potatoes or other plain vegetables. Speedy and unusual, the soft pink topping retains a full, buttery savor, while the tamarillo adds overtones of nutmeg, raspberry, and allspice. Quite a remarkable transformation—and a good beginning for the tamarillo-shy.