Grapefruit Marmalade with Vanilla and Anise

Using a sharp knife, remove peel and white pith from 1 grapefruit and thinly slice. Remove peel and white pith from remaining grapefruit and discard (you won’t want all of the peel and pith in the marmalade). Slice flesh of both grapefruits into rounds; remove any seeds.

Combine sliced peel, grapefruit, and star anise in a large saucepan; scrape in seeds from vanilla bean and add pod. Toss to combine; pour in 4 cups water and bring mixture to a boil. Reduce heat and gently simmer until reduced by three-quarters, about 1 1/2 hours. Add sugar, return to a simmer, and cook until mixture is thickened and juices are syrupy (mixture will set up when a small amount is spooned onto a cold plate), 1–1 1/2 hours longer.

Let marmalade cool slightly, then stir in lemon juice. Spoon into clean jars and let cool.

Marmalade can be made 2 months ahead. Cover and chill.