Vanilla bean accentuates the pears perfume, but is not essential. You can also tuck sprigs of thyme among the pears.
• 1/4 to 1/3 cup sugar
• 1/2 vanilla bean (optional)
• 1 1/2 pounds slightly-under-ripe, fragrant, medium pears, peeled if desired and halved though the stem
• 1 tablespoon fresh lemon juice
• 2 tablespoons water
• 2 tablespoon unsalted butter
Preheat oven to 375 degrees F. Place the sugar in a small bowl. With a thin, sharp knife, split the vanilla bean lengthwise in half and scrape out the seeds. Stir the seeds into the sugar.
Arrange the pears in a large baking dish, cut-side up. Drizzle the lemon juice evenly over the fruit, then sprinkle with the sugar. Nestle the vanilla pod among the fruit. Pour the water into the dish. Dot each pear with some butter.
Roast the pears 30 minutes brushing them occasionally with the pan juices. Turn the pears over and continue roasting, basting once or twice, until tender and caramelized, 25 to 30 minutes longer (if the pears are small, test for doneness after 35 or 40 minutes of cooking; a paring knife poked into the thickest part of one should meet with no resistance). Serve warm.