Preheat oven to 400°F.
Place the butter in the bottom of a shallow baking dish. Drain off 3/4 of the liquids from each can – pears should remain wet but not swimming in syrup. Add pears to the dish and season with lemon zest, nutmeg and crystallized ginger then roast 20 minutes. Serve warm pears with scoops of French vanilla ice cream on top, garnish with lemon twist.