Combine apricots, water, vanilla bean, and sugar in a heavy one-quart saucepan. Bring to a boil, then reduce to a simmer, and cook, covered, for about 15 minutes.
Drain apricots, reserving the liquid; discard vanilla bean. Scrape mixture into blender or food processor. Add lemon juice and purée until smooth. Add remaining liquid to thin it to your taste.
If cooking in a microwave
Combine apricots, water, vanilla bean, and sugar in a 4-cup measure. Cover tightly with microwave plastic wrap. Cook for 7 minutes in a 650- to 700-watt oven or a shorter time in a more powerful one. Remove from oven and prick plastic to release steam. Follow steps from above step two.
Adapted from Barbara Kafka’s Microwave Gourmet (1989)