Place the pears in a non-aluminum saucepan large enough to hold them lying down. Add the wine, sugar, lemon zest, vanilla bean, and the water.

Place the pan over medium-high heat and bring to a boil. Reduce the heat to medium-low, set a heatproof plate on top of the pears to keep them submerged in the liquid, and simmer gently until a thin knife inserted into the widest part of a pear pierces easily to the center, 35-40 minutes. Remove the plate covering the pears. Let the pears cool to room temperature in the liquid.

Meanwhile, make a raspberry purée. In a food processor or blender, purée the 1 cup (4 oz/125 g) fresh or frozen berries until smooth. Pass the purée through a fine-mesh sieve held over a bowl, pressing the back of a wooden spoon to push as much of the purée through the sieve as possible. Discard the contents of the sieve. Set the purée aside.

Using a slotted spoon, lift the pears from the liquid. Set each pear in a shallow individual bowl, or place all four pears on a deep platter. Remove the zest and vanilla bean and discard or save the vanilla bean to garnish, if you like. Drizzle the raspberry purée onto the plate and garnish with a few fresh raspberries. Serve at room temperature.

SERVING TIP:
Pass out thin wafers of bittersweet chocolate to accompany the ruby pears.