Cut each pear in half lengthways, and remove the cores.
Sprinkle the sugar over the base of a large, preferably non-stick, fry pan. Add the butter and heat until the sugar has dissolved into the melted butter. Quickly add in the pears and caramelise until they are soft but still firm and holding their shape. This will take about 10 minutes and you should toss them occasionally. Add the prunes and fry for another minute or so. Now pour in the wine, but be careful as it will spit, so hold the pan away from you, then put it back over a lower heat. Split the vanilla pod in half lengthways using the tip of a sharp knife. Scrape the seeds out into the pan, also with the knife, then toss in the pod and let everything infuse for about 5 minutes.
Lift out the pears and prunes and set aside, then reduce the wine until it is good and gooey and thick, for about 8-10 minutes. That’s it really. Just pop the fruit back in and serve hot or cold with the lemon zest on top.
Making sugared lemon zest
Peel 2 lemons with a vegetable peeler, into a pan. Blanch the zest twice: cover with water, bring to boil, drain and repeat. Meanwhile, juice the lemons and make a syrup by heating the juice and 100g/4oz light muscovado sugar in a small pan until the sugar has dissolved. Simmer the blanched zest for 10 minutes with the syrup, then lift out with a slotted spoon, drain and dry on paper towel.