Remove any leaves from the rhubarb and trim the bases. Cut into 3cm lengths and put them into a large ovenproof dish. Scatter the sugar and zest on top and turn it all over with your hands.
Pour in the Damson Gin, orange juice and 2 tbsps water then tuck the rosemary sprigs under the rhubarb.
Cover tightly with foil then bake for about 10 minutes until the rhubarb is tender but holding its shape and not collapsing.
Remove from the oven and leave to cool a bit in the dish. Eat warm, at room temperature or chilled, with whipped cream or pouring cream.