Heat the oven to 400°F. Arrange the pear halves cut-side up in a 9x13-inch baking dish.
In a small bowl, stir the honey, melted butter, cinnamon and salt; brush half of it over the pears.
Roast 20-25 minutes, until a knife slides easily into the thickest part, basting once with the pan juices halfway through.
Meanwhile, toast the walnuts in a dry skillet over medium heat 3-4 minutes, stirring, until fragrant. Stir the vanilla into the yogurt.
Serve the warm pears with the yogurt, toasted walnuts and a drizzle of the remaining honey mixture.