Place the rhubarb and orange in a saucepan, cover with the zest, sugar and rosemary plus 100ml of water. Bring to the boil, then simmer for about 15 minutes until the fruit has collapsed and the juices resemble a light syrup- remember, the juice will thicken when cool. Press though a sieve- but juice only, don’t force the pulp through. Cool, cover and chill until needed.
250g rhubarb, trimmed and cut into small pieces
250g orange segments
the shredded zest of 2 oranges
250g caster sugar
1 sprig rosemary